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Solid-State Laser Spectra-Physics Opal User Manual

Femtosecond synchronously pumped optical parametric oscillator (sppo)
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Opal
Femtosecond Synchronously Pumped
Optical Parametric Oscillator (SPPO)
User's Manual
The Solid-State Laser Company
1335 Terra Bella Road
Mountain View, CA 94043
Part Number 0000-234A, Rev. E
September 2001

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  • Page 1 Opal Femtosecond Synchronously Pumped Optical Parametric Oscillator (SPPO) User’s Manual The Solid-State Laser Company 1335 Terra Bella Road Mountain View, CA 94043 Part Number 0000-234A, Rev. E September 2001...

  • Page 3: Preface

    Preface This manual contains information you need to safely install, align, operate, ® maintain, and service your Opal femtosecond synchronously pumped optical parametric oscillator ( SPPO The introductory chapter contains a brief description of the Opal and where it fits in with the Tsunami ®...
  • Page 4 Opal fs Synchronously Pumped Optical Parametric Oscillator This equipment has been designed and tested to comply with the limits for a Class A digital device pursuant to Part of the Rules. Finally, if you encounter any difficulty with the content or style of this manual, please let us know.

  • Page 5: Environmental Specifications

    Environmental Specifications CE Electrical Equipment Requirements For information regarding the equipment needed to provide the electrical service listed under “Service Requirements” at the end of Chapter 3, please refer to specification Plug, Outlet and Socket Couplers for Indus- EN-309, “ trial Uses listed in the official Journal of the European Communities.

  • Page 7: Table Of Contents

    Table of Contents Preface ............. . iii Environmental Specifications.
  • Page 8 Opal fs Synchronously Pumped Optical Parametric Oscillator Chapter 4: Controls, Indicators and Connections ......4-1 Opal Head .
  • Page 9 Table of Contents Scanning Coarse Length Menu (SETUP) ......... . . 6-16 Configure Menu (CONFIGURE) .
  • Page 10 Opal fs Synchronously Pumped Optical Parametric Oscillator List of Figures Figure 1-1: The Opal shown as part of a complete system. Included are a BeamLok 2080 pump laser, a Tsunami Lok-to-Clock pump laser, the Opal and the Opal Doubler. Also shown is the Model 409-08 autocorrelator........1-2 Figure 2-1: These CE and CDRH standard safety warning labels would be appropriate for use as entry warning signs (EN 60825-1, ANSI 4.3.10.1).
  • Page 11 Table of Contents List of Tables Table 2-1: Label Translations ............2-7 Table 3-1: Opal Specifications .
  • Page 12 Opal fs Synchronously Pumped Optical Parametric Oscillator...

  • Page 13: Warning Conventions

    Warning Conventions The following warnings are used throughout this manual to draw your attention to situations or procedures that require extra attention. They warn of hazards to your health, damage to equipment, sensitive procedures, and exceptional circumstances. All messages are set apart by a thin line above and below the text as shown here.

  • Page 15: Standard Units

    Standard Units The following units, abbreviations, and prefixes are used in this Spectra- Physics manual: Quantity Unit Abbreviation mass kilogram length meter time second frequency hertz force newton energy joule power watt electric current ampere electric charge coulomb electric potential volt Ω...

  • Page 17: Unpacking And Inspection

    Unpacking and Inspection Unpacking Your Laser ® Your Opal laser accessory was packed with great care and all containers were inspected prior to shipment: the Opal left Spectra-Physics in good condition. Upon receipt of your system, immediately inspect the out side of the shipping containers.

  • Page 19: Chapter 1: Introduction

    Chapter 1 Introduction ® The Opal SPPO Optical parametric oscillators ( s) were first used in the mid-1960's as an alternative to dye lasers for generating coherent radiation tunable over a wide wavelength region. It is only recently, however, that they have become a practical reality with the advent of new, high-quality, nonlinear optical materials and high-power, mode-locked pump sources.

  • Page 20: Patents

    Opal fs Synchronously Pumped Optical Parametric Oscillator Figure 1-1: The Opal shown as part of a complete system. Included are a BeamLok 2080 pump laser, a Tsunami Lok-to-Clock pump laser, the Opal and the Opal Doubler. Also shown in the upper right corner is the Model 409-08 autocorrelator.

  • Page 21: Configurations

    Introduction Configurations The Opal is available in two configurations: • Opal-1.3 µm, which provides a signal wavelength from 1.1 to 1.35 µm • Opal-1.5 µm, which provides a signal wavelength from 1.35 to 1.60 µm If you purchased any of the above configurations and require operation in another wavelength range, the following wavelength conversion sets are available: •...
  • Page 22 Opal fs Synchronously Pumped Optical Parametric Oscillator...

  • Page 23: Chapter 2 Laser Safety

    Chapter 2 Laser Safety and the Millennia ® The Opal ® , Tsunami ® pump laser are Class IV— Danger! High Power Lasers that have output beams that are, by definition, safety and fire hazards. Take precautions to prevent exposure to direct and reflected beams.

  • Page 24: Figure 2-2: Folded Metal Beam Target

    Opal fs Synchronously Pumped Optical Parametric Oscillator • Establish a controlled access area for laser operation. Limit access to those trained in the principles of laser safety. • Post prominent warning signs near the laser operation area (Figure 2- • Set up experiments so the laser beam is either above or below eye level.

  • Page 25: Safety Devices

    Laser Safety Safety Devices Shutter Interlock Because the energy to drive the process in Opal comes from another laser and not from an internal source (such as electrical discharge), the interlock differs slightly from that of solid-state or ion lasers. The Opal has a single shutter interlock that blocks the pump beam at the entrance to the housing to prevent lasing.

  • Page 26: Maintenance Required To Keep This Laser Product In Compliance With Center For Devices And Radiological Health (Cdrh) Regulations

    Opal fs Synchronously Pumped Optical Parametric Oscillator Maintenance Required to Keep this Laser Product in Compliance with Center for Devices and Radio- logical Health ( ) Regulations CDRH This section presents the maintenance required to keep this laser accessory product in compliance with Regulations.

  • Page 27: Ce/Cdrh Radiation Control Drawings

    Laser Safety CE/CDRH Radiation Control Drawing Input Opal Output REPLACE THE BATTERY WITH THE SAME OR EQUIVALENT TYPE RECOMMENDED BY THE MANUFACTURER. DISPOSE OF USED BATTERIES ACCORDING TO THE MANUFACTURER'S INSTRUCTIONS. WAVELENGTH POWER Spectra-Physics STABILIZED MONITOR MONITOR TO OPAL HEAD MODEL NUMBER HEATER...

  • Page 28: Figure 2-5: Ce/Cdrh Warning Labels

    Opal fs Synchronously Pumped Optical Parametric Oscillator CE/CDRH Warning Labels Spectra-Physics 1344 TERRA BELLA AVENUE MT. VIEW, CALIFORNIA 94039 Spectra-Physics MANUFACTURED: YEAR MONTH MODEL NUMBER MODEL SERIAL NUMBER THIS LASER PRODUCT COMPLIES WITH 21 CFR 1040 AS APPLICABLE. MADE IN U.S.A. 404-471 MADE IN U.S.A.

  • Page 29: Label Translations

    Laser Safety Label Translations For safety, the following translations are provided for non-English speak- ing personnel. The number in parenthesis in the first column corresponds to the label number listed on the previous page. Table 2-1: Label Translations Label # French German Spanish...

  • Page 30: Ce Declaration Of Conformity (Emissions)

    Opal fs Synchronously Pumped Optical Parametric Oscillator CE Declaration of Conformity Spectra-Physics, Inc. Scientific and Industrial Systems 1330 Terra Bella Avenue P.O. Box 7013 Mountain View, CA. 94039-7013 United States of America declare under sole responsibility that the: OPAL, cw/Pulsed Optical Parametric Oscillator with Controller, Manufactured after December 31, 1996 meet the intent of “Directive for Electromagnetic Compatibil-...
  • Page 31 Laser Safety EC Declaration of Conformity Spectra-Physics, Inc. Industrial and Scientific Lasers 1330 Terra Bella Avenue P.O. Box 7013 Mountain View, CA. 94039-7013 United States of America declare under sole responsibility that the OPAL, cw/Pulsed Optical Parametric Oscillator with Controller, meets the intent of “Directive , the Low Voltage directive.”...

  • Page 32: Sources For Additional Information

    Opal fs Synchronously Pumped Optical Parametric Oscillator Sources for Additional Information The following are some sources for additional information on laser safety standards, safety equipment, and training. Laser Safety Standards Safe Use of Lasers (Z136.1: 1993) American National Standards Institute ( ANSI 11 West 42 Street...

  • Page 33: Equipment And Training

    Laser Safety Equipment and Training Laser Safety Guide Laser Institute of America 12424 Research Parkway, Suite 125 Orlando, FL 32826 Tel: (407) 380-1553 Laser Focus World Buyer's Guide Laser Focus World Penwell Publishing 10 Tara Blvd., 5 Floor Nashua, NH 03062 Tel: (603) 891-0123 Lasers and Optronics Buyer's Guide Lasers and Optronics...
  • Page 34 Opal fs Synchronously Pumped Optical Parametric Oscillator 2-12...

  • Page 35: Chapter 3: Opal Description

    Chapter 3 Opal Description OPOs Since the early 1990s, the mode-locked Ti:sapphire laser has become the system of choice for ultrafast laser applications. The Spectra-Physics Tsu- ® nami mode-locked Ti:sapphire oscillator provides the most flexible com- mercial system with (i) wavelength coverage from 690 to 1080 nm, (ii) a pulse width range from <...

  • Page 36: Figure 3-1: A Typical Optical Parametric Oscillator Configuration

    Opal fs Synchronously Pumped Optical Parametric Oscillator Output Coupler Signal Output Pump Input Non-Linear Crystal High Reflector Idler Output Figure 3-1: A Typical Optical Parametric Oscillator Configuration ω idler ω ω 2ω pump ω signal ω Second Harmonic Generation Parametric Down Conversion Figure 3-2: Optical frequency three-wave conversion process Momentum conservation, is achieved by using a birefringent nonlinear crystal and by satisfying the...

  • Page 37: The Opal

    Description to that of the Ti:sapphire pump laser, so that the signal and pump pulses are always present in the nonlinear crystal at the same time). The pioneering work on fs s systems was done at Cornell University SPPO in the laboratory of Professor C. L Tang using angle-tuned potassium tita- nyl phosphate ( ) as the nonlinear gain medium.

  • Page 38: Wavelength Tuning Characteristics

    Opal fs Synchronously Pumped Optical Parametric Oscillator Wavelength Tuning Characteristics The Opal can be pumped at any wavelength between 720 and 850 nm with 2 W of average power and 100 fs pulse widths at a repetition rate of about 80 MHz.

  • Page 39: Configuration

    Description For the 1.35 to 1.60 µm signal wavelength region, 810 nm is used for the pump wavelength. Since the crystal exhibits negative in the sig- nal wavelength range, it is not necessary to use prisms for the 1.5 µm optics set.

  • Page 40: The Opal Electronics Module

    Opal fs Synchronously Pumped Optical Parametric Oscillator The Opal Electronics Module The Opal electronics module is designed for easy operation. The tempera- ture of the crystal and the entire servo system, including the cavity length adjustments, are microprocessor controlled. This allows for auto- mated wavelength tuning and automated setup via a simple menu-driven program.

  • Page 41: Figure 3-7: Wavelengths Most Affected By Vapor Absorption

    Description 1.100 1.200 1.300 1.400 1.500 1.600 Wavelength (µm) Figure 3-7: Wavelengths most affected by vapor absorption...

  • Page 42: Opal Specifications

    Opal fs Synchronously Pumped Optical Parametric Oscillator Opal Specifications Table 3-1: Opal Specifications Output Characteristics Opal Performance (Signal Output) 1.3 µm with 1.5 µm with 775 nm pump 810 nm pump >150 mW >150 mW Average Power <130 fs <130 fs Pulse Width 1.10–1.35 µm 1.35–1.60 µm...

  • Page 43: Outline Drawings

    Description Outline Drawings 12.24 (31.09) 1.50 8.50 3.60 5.29 36.00 (9.14) (13.44) (3.81) (21.60) (91.44) 7.62 (19.35) 4.43 4.50 1.13 (11.25) (11.43) (2.86) 4.00 0.9 to 1.5 (10.16) 2.15 8.00 24.00 3.75 (2.3 to 3.8) (5.46) (20.32) (60.96) (9.53) OPAL (Input End) OPAL (side view) OPAL (Output End) 17.00...
  • Page 44 Opal fs Synchronously Pumped Optical Parametric Oscillator 3-10...

  • Page 45: Chapter 4: Controls, Indicators And Connections

    Chapter 4 Control, Indicators and Connections This section defines the user controls, indicators and connections of the ® Opal system, and it is divided into two main sections: the Opal Head and the Opal Electronics Module. Refer to Figure 4-1, Figure 4-3 and Figure 4-4. Opal Head Figure 4-1 shows the location of the controls and connections on the Opal head.

  • Page 46: Input Bezel Connections

    Opal fs Synchronously Pumped Optical Parametric Oscillator Input Bezel Connections The input bezel connections attach to the Opal electronics module and to a nitrogen purge supply source, usually to a Model 3910 filter/drier unit. Purge bleeder valve—when open, allows more purge gas to flow through the Opal head when the system is first turned on.
  • Page 47 Controls, Indicators and Connections Iris —facilitates in aligning the Opal pump beam. It has a lever to set the iris size. Do not move the mount from its factory-set position or you will be unable to properly align the system. Pump beam mirror —directs the pump beam onto focus mirror .
  • Page 48 Opal fs Synchronously Pumped Optical Parametric Oscillator Servo wavelength monitor—contains a stepper-driven grating and a bi- cell sensor. Using microprocessor control, this assembly monitors and sets the output wavelength by actively stabilizing the cavity length. The error signal for cavity length stabilization is provided by ratioing the signals from each half of the bi-cell.

  • Page 49: Opal Electronics Module

    Controls, Indicators and Connections Residual pump mirror —directs the residual Ti:sapphire pump (RPM) beam reflected from the input surface of the crystal through the focus- ing lens and out the Residual Pump Port Output window. It has vertical and horizontal adjustments. When absent, a beam block contains the residual beam.

  • Page 50: Rear Panel

    Opal fs Synchronously Pumped Optical Parametric Oscillator Rear Panel Figure 4-4 shows the location of the various cables and switches on the Opal electronics rear panel. On/off power switch—turns on and off power to the electronics module. Power cord connector—provides connection for the power cord. On/Off Switch Power Cord...
  • Page 51 Controls, Indicators and Connections connector ( )—provides a buffered signal from the POWER MONITOR output power monitoring circuit that can be used to monitor the Opal out- put power level. connector (D-Sub)—provides connection for drive and TO OPAL HEAD feedback signal cable that attaches to the output bezel of the Opal head. connector—provides connection for the heater drive and feed- HEATER back cable that attaches to the output bezel of the Opal head.
  • Page 52 Opal fs Synchronously Pumped Optical Parametric Oscillator...

  • Page 53: Chapter 5: Installation And Alignment

    Chapter 5 Installation and Alignment ® This chapter contains installation and alignment procedures for the Opal. A Spectra-Physics service representative will perform the initial system alignment and cleaning at the time of installation. Thereafter, there should be little need to do a full alignment. The “Cavity Alignment” section is pro- vided in the event either a gross misalignment has occurred or you need to convert from 1.3 to 1.5 µm operation, or vice versa.

  • Page 54: Setting Up The System

    Opal fs Synchronously Pumped Optical Parametric Oscillator Setting up the System Most of the tools, signal cables, and equipment you need to set up the Opal are in your accessory kit. Place the Opal head 12 cm in front of the Tsunami laser head as shown in Figure 5-1, such that the input port is directly in line with the Tsu- nami output port.

  • Page 55: Removing/Installing The Lbo Crystal

    Installation and Alignment Removing/Installing the LBO Crystal Skip this section if the crystal is already installed, but please read the warn- ing statement below about safeguarding your expensive crystal from mois- ture damage. Warning! Due to the hygroscopic nature of the crystal, you must keep the crystal contained in a dry environment at all times and minimize the exposure time to the environment, even during installation.
  • Page 56 Opal fs Synchronously Pumped Optical Parametric Oscillator Note the location of the crystal tower with regard to the dovetail base. Removing the Crystal Assembly 1. Adjust the Tsunami for about 200 mW of output power. Reduce iris to a minimum. 3.

  • Page 57: Aligning The Opal Head

    Installation and Alignment Adjusting the Crystal Temperature and Offset This process sets the crystal temperature to the factory setting. By first adjusting the table offset to obtain the correct temperature at the tested wavelength, a minimum amount of point offset can be retained. Verify the current wavelength is the same as the test wavelength noted on the crystal test summary.
  • Page 58 Opal fs Synchronously Pumped Optical Parametric Oscillator a. Install the single-plate birefringent filter as the tuning element. This replaces the slit assembly. The filter is included in the Opal accessory kit. Refer to the sections on removing the slit assembly and installing the birefringent filter in your Tsunami User's Man- ual.

  • Page 59: Attaching The Opal Purge Line

    Installation and Alignment Idler Idler Waveplate Output Input Residual Pump Port Servo Lens Idler Output Wavelength Aperture Monitor Assy. Output Coupler Signal Output Beam Splitter Motor-controlled Mirror * Crystal Assembly Figure 5-2: Opal Cavity Layout e. Keep centered on the beam and move the Opal output end hori- zontally so that the head is roughly parallel to the beam.

  • Page 60: Figure 5-3: Transmittance Vs. Wavelengths For Water Vapor In The Opal Signal Wavelength Range

    Opal fs Synchronously Pumped Optical Parametric Oscillator 1.100 1.200 1.300 1.400 1.500 1.600 Wavelength (µm) Figure 5-3: Transmittance vs. wavelengths for water vapor in the Opal Signal wavelength range To purge the Tsunami laser and the Opal at the same time, perform the fol- lowing to insert the T-connector into the Model 3910 output purge line.

  • Page 61: Removing The Opal Purge Line

    Installation and Alignment Warning! Always use dry, oil-free, Electronic Grade 5 (or better) nitrogen (99.999% pure) to prevent contamination of the system. Do not purge with nitrogen from a boil-off tank or other non-approved gas source. Do not connect to any source with a pressure greater than 67 kPa (10 psi) or damage to the Model 3910 filters will result.

  • Page 62: Figure 5-5: P And M Spacing

    Opal fs Synchronously Pumped Optical Parametric Oscillator Example: If the Tsunami repetition rate is 80.150 MHz, its effec- tive cavity length L is 150 divided by 80.150, or 1.871 meters. Warning! The spacing between is factory set and should never require realignment.

  • Page 63: Aligning The Pump Beam

    Installation and Alignment f. Subtract the total measured distance of the Opal cavity length from that of the Tsunami laser (i.e., find the difference between the two). g. Loosen the two large Allen (hex) screws that secure the mount to the base plate of the Opal, and slide the mount to the point where the Opal cavity length matches that of the Tsunami.

  • Page 64: Aligning The Opal Cavity

    Opal fs Synchronously Pumped Optical Parametric Oscillator amount of reflectance. The beam should be close to the center of the crystal. Do not move the beam near the edge of the crystal! a. Loosen the setscrew that locks the translation stage in place just enough so that the stage can be translated.
  • Page 65 Installation and Alignment Close a little to verify the beam is centered. Iterate between adjust- ments of to center the beam through and onto Adjust vertically and horizontally to reflect the blue beam back through the center of iris , then fully open Adjust to direct the blue beam through iris and onto the center of...

  • Page 66: Alignment Of Pr And Pr Prism Sequence

    Opal fs Synchronously Pumped Optical Parametric Oscillator b. If a flash is observed, move back to the position that produced it and skip to Step 20. c. If no flash is observed by the time has reached the end of its travel, translate it in the other direction until a flash is observed.

  • Page 67: Completing The Cavity Alignment

    Installation and Alignment the secondary cavity. Continue to insert until a visible flash is observed, then optimize for sustained lasing action. b. If the Opal fails to flash in Step a, repeat Steps 4 and 5. Note: verti- cal alignment is easily verified by noting the position of the hori- zontal line on the card.

  • Page 68: Aligning The Beam To The Servo Wavelength Monitor Assembly

    Opal fs Synchronously Pumped Optical Parametric Oscillator 7. Once you observe the flash, translate slightly so you get sustained oscillation. Place a power meter in front of the Signal output window. 9. Translate slightly, back and forth, until you find the point for maxi- mum output power.

  • Page 69: Completing The Alignment

    Installation and Alignment b. Center the beam vertically by making very small adjustments to , and . Do not lose oscillation–use the Manual Control menu to adjust the position of for maximum output power after each incremental adjustment. Beam Post Grating Figure 5-7: Positioning the Signal beam horizontally on the grating.

  • Page 70: Table 5-1: Typical Settings For Opal Output At 1.300 Μm

    Opal fs Synchronously Pumped Optical Parametric Oscillator Replace the Opal cover. Make sure you do not bump any control knobs. From the Setup menu, verify the operating parameters are correct, i.e., the Tsunami pump wavelength and the Opal optics set is correctly selected, then run the command.

  • Page 71: Opal Alignment-1.5 Μm Optic Set

    Installation and Alignment Opal Alignment—1.5 µm Optic Set The 1.5 µm optic set is used when the desired Signal wavelength output is between 1.35 and 1.6 µm. The alignment procedure for the 1.5 µm optics set uses a similar procedure to the 1.3 µm optic set, but it is not necessary to employ prisms in the cavity.

  • Page 72: Aligning The Pump Beam

    Opal fs Synchronously Pumped Optical Parametric Oscillator a. From the Setup menu, initiate a command. This Scan Length ensures the software recognizes the polarity of the motor. b. Set to the center of its range. Use the Manual Control menu and the up/down push buttons on the electronics module to set to a 50% value.

  • Page 73: Aligning The Opal Cavity

    Installation and Alignment Close the iris a little to verify the beam is centered. Note the even ring around the opening when it is centered. If necessary, repeat these last steps, starting at Step 3, until this condition is achieved. Adjust horizontally and vertically to direct the pump beam onto the center of...
  • Page 74 Opal fs Synchronously Pumped Optical Parametric Oscillator To increase the intensity of the second harmonic beam, remove the output coupler at and replace it with the additional high reflector (provided in your optics kit). Less loss will aid in the initial alignment. Remember to close the shutter while changing optics.

  • Page 75: Completing The Cavity Alignment

    Installation and Alignment 19. Scan to obtain a flash. a. From the Manual Control menu, select on the same menu Motor and press the down button to the right of the display to move toward one end of its range. Watch for a flash. During translation, a flash of green or orange light should appear within the cavity.

  • Page 76: Aligning The Beam To The Servo Wavelength Monitor

    Opal fs Synchronously Pumped Optical Parametric Oscillator a. If you do not observe a flash, replace the output coupler with the high reflector, then reoptimize the cavity for maximum intracavity visible light generation. To do this, adjust , and , and make small translational adjustments of with the motor control.

  • Page 77: Completing The Alignment

    Installation and Alignment Using an ir detector, verify the Signal beam reflected from the front surface of the beam splitter is centered on the grating in the servo housing. The beam spot should be positioned on the grating as shown in Figure 5-7.

  • Page 78: Table 5-2: Typical Settings For Opal Output At 1.500 Μm

    Opal fs Synchronously Pumped Optical Parametric Oscillator From the Main menu, adjust the output wavelength to 1.500 µm using the up/down keys. 6. Use a monochromator to measure the output Signal wavelength. If the wavelength readout differs from your actual measured wave- length by more than ±3 nm perform the following.

  • Page 79: Converting From 1.3 To 1.5 Μm

    Installation and Alignment Converting from 1.3 to 1.5 µm The following procedure allows you to change optics sets from 1.3 µm to 1.5 µm operation. Close the Opal shutter. Back out of the beam path to allow an unobstructed beam path from Remove mirrors through...

  • Page 80: Converting From 1.5 To 1.3 Μm

    Opal fs Synchronously Pumped Optical Parametric Oscillator Converting from 1.5 to 1.3 µm The following procedure allows you to change optics sets from 1.5 µm to 1.3 µm operation. Close the Opal shutter. Remove mirrors through and place them in their protective stor- age containers.

  • Page 81: Chapter 6: Operation

    Chapter 6 Operation Warning! memory card in the Opal controller uses a 3 V disk battery PCMCIA to maintain the data stored in it. The expected lifetime of the battery is approximately 2–3 years, so it is prudent to change the battery every 2 years regardless of use.

  • Page 82: Turning On The System

    Opal fs Synchronously Pumped Optical Parametric Oscillator When the wavelength is selected, the computer calculates the appropriate temperature for the crystal based on the known Tsunami pump wavelength, and the Opal cavity length is automatically adjusted through the grating/bi- cell servo system. The servo system provides a measurement of the signal wavelength and is calibrated automatically by the Opal electronics module each time is performed from the Setup menu during start-up.

  • Page 83: Table 6-1: Typical Settings For Several Opal Wavelengths

    Operation Table 6-1: Typical Settings for Several Opal Wavelengths Nom. Crystal Opal Pump Nom. Grating Wavelength (µm) Wavelength (nm) Setting (steps) Temperature 1.100 3673 1.150 3420 1.200 3166 1.250 2910 1.300 2652 1.350 2390 1.400 2128 1.450 1832 1.500 1596 1.550 1327 1.600...

  • Page 84: Resetting The Wavelength

    Opal fs Synchronously Pumped Optical Parametric Oscillator To optimize the pulse width of the signal, use the Adjust Temp menu and make small temperature adjustments while monitoring the pulse width with an autocorrelator. If the 1.3 µm optic set is installed, use the micrometer adjust on prism to vary the amount of prism glass in the intracavity beam.

  • Page 85: Purging The Opal

    Operation Purging the Opal The Opal is sealed so that it can be purged with nitrogen gas. Purging the cavity not only eliminates the typical problems associated with dust and contamination, but also prevents tuning discontinuities caused by oxygen and water vapor. Purging of the latter is imperative for operation between 1.33 and 1.48 µm, and when operating below 1.18 µm (Figure 6-1).

  • Page 86: Purge Turn-On

    Opal fs Synchronously Pumped Optical Parametric Oscillator Purge Turn-on Verify the Opal cover is in place and clamped down, sealing the cavity. Verify the nitrogen tank output regulator is set to minimum, then turn on the nitrogen supply. Set the bottle output regulator to limit pressure to less than 67 kPa (10 psi).

  • Page 87: The Menus

    Operation When present, the soft key allows you to toggle (move) the indi- Next Field cator highlight box to place it around a field variable you wish to change (power level, crystal temperature, wavelength, position, etc.). The up/ down push-buttons to the right of the screen allow you to modify the con- tents or value of the selected field.

  • Page 88: Figure 6-2: Flowchart Of The Opal Electronics Module Menu System

    Opal fs Synchronously Pumped Optical Parametric Oscillator MAIN Main Menu 1.500 L 1.761µm Power Scan Remote Setup Config Ctrl Temp SCAN REMOTE CONFIGURE DIAGNOSTICS Scan Remote Configure SCAN Signal Idler 1.500 CONFIGURE from 1.300 2.149µm to 1.620 1.620µm 1.761µm µm step 0.001 dwell 0.5 Please select a...

  • Page 89: Main Menu (Main)

    Operation Main Menu (MAIN) 1.500 L 1.761µm Power Scan Remote Setup Config Ctrl Temp The Main menu is at the top of the menu structure and is displayed at start- up immediately following the Spectra-Physics logo. It is the default screen for monitoring the system.

  • Page 90: Scan Menu (Scan)

    Opal fs Synchronously Pumped Optical Parametric Oscillator Scan Menu (SCAN) SCAN Signal Idler from 1.350 2.025µm 1.835µm to 1.450 µm step 0.001 dwell 0.5 times Next Start Main Field Scan Menu The Scan menu reports to the Main menu. It allows the operator to scan a selected number of times through a wavelength region in selected incre- mental step size, and have the system stop (dwell) for a selected time period at each step.

  • Page 91: Scan Status Menu (Scan)

    Operation Scan Status Menu (SCAN) 1.360 Scanning Signal from 1.350µm to 1.450µm 2.003µm SCAN # 1 Pause Scan The Scan Status menu reports to the Scan menu. It displays the status of the scan, showing the Signal wavelength limits set in the Scan menu as well as the relative position of the scan within those limits.

  • Page 92: Remote Menu (Remote)

    Opal fs Synchronously Pumped Optical Parametric Oscillator Remote Menu (REMOTE) 1.500 1.761µm Please select a Power PZT remote control mode RS232 IEEE Local Ctrl The Remote menu reports to the Main menu. It allows the control interface to be set to , or .
  • Page 93 Operation temperatures or to a set of temperatures which have been optimized under the single point offset procedure (see below). Also, once a single point off- set procedure has been implemented, the temperature table shift option is useful to fine-tune the system for optimum performance on a day-to-day basis.

  • Page 94: Clear Menu (Adjust Temperature)

    Opal fs Synchronously Pumped Optical Parametric Oscillator Soft Keys: —moves the highlight box surrounding the field to the Next Field Signal field and back again so that the wavelength or Temp Table/Single Point Offset temperature variable can be changed using the up/down push-buttons. —allows the temperature setpoint to be changed by either shift- Shift/Point ing the entire table (all points are offset in the same direction by the same...

  • Page 95: Setup Menu (Setup)

    Operation Setup Menu (SETUP) SETUP Optics set: 1.3-1.6 810 nm pump assumed Check that Tsunami is at 810 nm Next Full Scan Main Field Align Length Menu The Setup menu reports to the Main menu. Through it the optics set is specified and the pump wavelength is selected.

  • Page 96: Scan Length Menu (Setup)

    Opal fs Synchronously Pumped Optical Parametric Oscillator Scan Length Menu (SETUP) Preparing to scan length Desired xtal temp is 63.6% Actual temp is 13.9% Abort The Scan Length menu reports to the Setup menu. When it appears, it dis- plays a notice that the length scan is about to begin, and also shows the desired temperature and actual temperature of the crystal in percent of total range.

  • Page 97: Configure Menu (Configure)

    Operation Configure Menu (CONFIGURE) CONFIGURE Save/ Misc. Diag- Go to Main Recal nostics Idle menu The Configure menu reports to the Main menu and allows the operator to save and recall system settings, run Opal diagnostics, and set the Opal to for overnight stand-by mode.

  • Page 98: Miscellaneous (Configuration)

    Opal fs Synchronously Pumped Optical Parametric Oscillator Soft Keys: —stores one set of scan parameters with optimized temperature off- Save sets for later use. The information is stored in the memory location desig- nated by the number shown in the menu. The memory location is changed using the up/down push-buttons.

  • Page 99: Diagnostics Menu (Diagnostics)

    Operation Diagnostics Menu (DIAGNOSTICS) DIAGNOSTICS Temperature: 57.5% Servo Setpoint:1.500 (2168cts) Motor Position: 50.2% Loop is ON Manual Cal. About Main Ctrl Wavelen Opal menu The Diagnostics menu reports to the Configure menu. It displays critical operating parameters and the system status. Through the Manual Control menu the operator can set the temperature of the crystal, set the wave length (grating angle) or step setting, set the position, and turn the servo...
  • Page 100 Opal fs Synchronously Pumped Optical Parametric Oscillator graph. Parameter fields that can be changed using the soft key Next Field are: • crystal temperature (in percent of total range) • wavelength or step count grating angle (toggle) • position, and •...

  • Page 101: Scanning Coarse Length Menu (Diagnostics)

    Operation Scanning Coarse Length Menu (DIAGNOSTICS) SCANNING COARSE LENGTH Scanning reverse.. Abort Scan The Scanning Coarse Length menu reports to the Manual Control menu. It dynamically displays a scan search for the Tsunami/Opal cavity match point, i.e., the point where the Opal cavity matches that of the Tsunami laser or where the round-trip time of the signal pulse in the Opal cavity matches that of the pump pulse in the Tsunami.
  • Page 102 Opal fs Synchronously Pumped Optical Parametric Oscillator 6-22...

  • Page 103: Chapter 7: Maintenance

    Chapter 7 Maintenance The condition of the laboratory environment and the amount of time the ® Opal is operated affects its periodic maintenance schedule. The coated surfaces of the elements forming the cavity—the output coupler, high reflector, prisms, fold and focus mirrors—and crystal surfaces are easily contaminated.

  • Page 104: Equipment Required

    Opal fs Synchronously Pumped Optical Parametric Oscillator Equipment Required: • dry, filtered nitrogen or canned air • rubber squeeze bulb • optical-grade lens tissue • spectrophotometric-grade methanol and/or acetone (for general optics) • spectrophotometric-grade ( ) toluene or xylene (Aldrich Gold HPLC Label) for cleaning the crystal •...

  • Page 105: Standard Cleaning Procedures

    Maintenance Each optical element has a v-shaped arrow on its barrel. This arrow points to the coated surface that faces the intracavity beam. Also written on the barrel is the optic part number. If you need to verify the location of the optic in the Opal, refer to the part number list for each optic in Table 8-1 at the end of Chapter 8, “Service and Repair.”...

  • Page 106: General Procedure For Cleaning All Optics Except The Crystal

    Opal fs Synchronously Pumped Optical Parametric Oscillator ™ • Use Kodak Lens Cleaning Paper (or equivalent photographic clean- ing tissue) to clean optics. • Use each piece of lens tissue only once; dirty tissue merely redistrib- utes contamination—it does not remove it. Do not use lens tissue designated for cleaning eye glasses.

  • Page 107: Figure 7-2: Tissue Folded For Cleaning

    Maintenance a. Hold the optic horizontal with its coated surface up. Place a sheet of lens tissue over it and squeeze a drop or two of acetone or meth- anol onto it. b. Slowly draw the tissue across the surface to remove dissolved con- taminants and to dry the surface.

  • Page 108: General Procedure For Cleaning The Crystal

    Opal fs Synchronously Pumped Optical Parametric Oscillator General Procedure for Cleaning the Crystal Clean the crystal only when you cannot obtain specified power (a) after cleaning all the other optics, (b) after performing the standard alignment procedure outlined in Chapter 6, “Operation: Turning On the System,” and (c) after translating the crystal so that the beam passes through a cleaner or undamaged area.

  • Page 109: Chapter 8: Service And Repair

    Chapter 8 Service and Repair This chapter contains a general troubleshooting guide for use by you, the user. It is provided to assist you in isolating some of the problems that might arise while using the system. A complete repair procedure is beyond the scope of this manual.
  • Page 110 Opal fs Synchronously Pumped Optical Parametric Oscillator Symptom: No flash when is initiated. Scan Length Possible Causes Corrective Action Incorrect software parameters Verify the proper parameters have been selected in the Setup menu for the have been selected. optics set used. Wave plate is in the beam.
  • Page 111 Service and Repair Symptom: Low Power Possible Causes Corrective Action Broaden the Tsunami pulse to ≈ 100 fs (about 9–10 nm FWHM of band- Tsunami pulse is too narrow. width). Low pump power. Allow the Millennia and Tsunami lasers to warm up about 10–15 min., then adjust both lasers for a 2 W output from the Tsunami.
  • Page 112 Opal fs Synchronously Pumped Optical Parametric Oscillator Symptom: Opal Flashes but will not lock when is initiated. Scan Length Possible Causes Corrective Action Misaligned servo grating wave- Refer to Appendix C for information on calibrating the servo grating wave length assembly. length assembly.
  • Page 113 Service and Repair Symptom: Noisy Opal output. Possible Causes Corrective Action Incorrect temperature offset. Set the temperature offset for optimum Opal performance. Refer to Chapter 6, “Operation: Adjust Temp Menu,” for information on why and how to set the crystal offset temperature. Noisy Tsunami laser.

  • Page 114: Replacement Parts

    Opal fs Synchronously Pumped Optical Parametric Oscillator Replacement Parts Table 8-1: Opal Standard Mirrors Description Location Coating Range Part Number Beam splitter Signal Output 1.3–1.5 µm G0020-000 Assembly, High Reflector PZT 1090–1370 nm 0449-1840 Assembly, High Reflector PZT 1320–1600 nm 0449-1850 Assembly, Crystal –...

  • Page 115: Chapter 9 Customer Service

    Chapter 9 Customer Service At Spectra-Physics, we take pride in the durability of our products. We place considerable emphasis on controlled manufacturing methods and quality control throughout the manufacturing process; nevertheless, even the finest precision instruments will need occasional service. We feel our instruments have excellent service records compared to competitive prod- ucts, and we hope to demonstrate, in the long run, that we provide above- average service to our customers—not only in providing the best equip-...

  • Page 116: Return Of The Instrument For Repair

    Opal fs Synchronously Pumped Optical Parametric Oscillator This warranty does not apply to any instrument or component not manufac- tured by Spectra-Physics. When products manufactured by others are included in Spectra-Physics equipment, the original manufacturer's war- ranty is extended to Spectra-Physics customers. When products manufac- tured by others are used in conjunction with Spectra-Physics equipment, this warranty is extended only to the equipment manufactured by Spectra- Physics.

  • Page 117: Service Centers

    Customer Service Service Centers Benelux Telephone: (31) 40 265 99 59 France Telephone: (33) 1-69 18 63 10 Germany and Export Countries Spectra-Physics GmbH Guerickeweg 7 D-64291 Darmstadt Telephone: (49) 06151 708-0 Fax: (49) 06151 79102 Japan (East) Spectra-Physics KK East Regional Office Daiwa-Nakameguro Building 4-6-1 Nakameguro...
  • Page 118 Opal fs Synchronously Pumped Optical Parametric Oscillator...

  • Page 119: Appendix A: Setting The Line Voltage Switch

    Appendix A Setting the Line Voltage Switch The line voltage switch, part of the power connector on the Opal electron- ics module, must match your local line voltage. The Opal electronics mod- ule is shipped from the factory with the line voltage selected for the location of intended use.

  • Page 120: Table A-1: Fuse Selection

    Opal fs Synchronously Pumped Optical Parametric Oscillator 3. Select the voltage. There are four voltage selections, one written on each edge of the pc board with a small arrow pointing to it. a. Measure your facility outlet voltage, then rotate the pc board until the edge with the measured voltage printed on it faces the inside of the module (arrow points into the module).

  • Page 121: Appendix B: Gvd Compensation

    Pulse Width Measurement Appendix B and GVD Compensation Introduction In this chapter we discuss how to measure pulses using an autocorrelator, as well as how to compensate for group velocity dispersion ( The Autocorrelation Technique Measurement of Ultrashort Pulses An autocorrelator is the most common instrument used for measuring an ultrafast femtosecond (fs) or picosecond (ps) optical pulse.

  • Page 122: Figure B-1: Interferometric (Collinear) Autocorrelation

    Opal fs Synchronously Pumped Optical Parametric Oscillator Photomultiplier Tube uv Filter Non-linear Crystal Lens Beam Splitter Incoming Beam Mirror Adjustable Delay Mirror Figure B-1: Interferometric (Collinear) Autocorrelation Photomultiplier Tube uv Filter Frequency-doubled Non-linear Autocorrelation Crystal Signal Lens Retro Prism Beam Splitter Incoming Beam Adjustable Delay...

  • Page 123: Figure B-3: The Model 409-08 Autocorrelator Optical Path. The Beam Paths Are

    GVD Compensation The Spectra-Physics Model 409-08 scanning autocorrelator operates in a background-free configuration according to the principles of noncollinear autocorrelation. It allows the autocorrelator signal to be conveniently dis- played on a high impedance oscilloscope, which provides the user with instantaneous feedback of laser performance.

  • Page 124: Signal Interpretation

    Opal fs Synchronously Pumped Optical Parametric Oscillator Signal Interpretation In order to determine the actual pulse width from the displayed autocorre- lation function, it is necessary to make an assumption about the pulse ∆ shape. Table B-1 shows the relationship between pulse width, , and the ∆...
  • Page 125 GVD Compensation Since most autocorrelators use beam splitters, a lens, and often a spinning block (as in the Spectra-Physics Model 409-08), the pulse is also broad- ened in the autocorrelator before it is measured. This means the pulse out of the Tsunami or Opal may be actually shorter than that indicated by direct measurement.

  • Page 126: Table B-2: Positive Dispersion Values @ 800 Nm

    Opal fs Synchronously Pumped Optical Parametric Oscillator The laser pulse travels through the first prism where different frequency components are spread in space. Then the broadened pulse travels through the second prism, strikes a high reflector, and reflects back along its origi- nal path—with one exception.

  • Page 127: Calculating Pulse Broadening

    GVD Compensation prism into the beam path and monitoring the pulse with a Model 409-08, the pulse should get narrower as dispersion is balanced. If a minimum can- not be found, adjust the prism spacing and search for the minimum again. Calculating Pulse Broadening Below are some simple formulae for calculating the effects of and its...

  • Page 128: Figure B-5: Broadening Curve

    Opal fs Synchronously Pumped Optical Parametric Oscillator 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 S (Normalized Units) Figure B-5: Broadening Curve Example 1: Calculating pulse width measured by a Model 409-08 without pre-compensation.
  • Page 129 GVD Compensation ω tot ω tot ω 1 ( ) ω 1 ( ) ω 2 ( ) ω 2 ( ) ω 3 ( ) ω 3 ( ) ω 4 ( ) ω 4 ( ) = 300 · 2.16 + 450 · 0.25 + 0.8 · 1590 + L · (–80.2) = 0 Therefore L = 25.3 cm.
  • Page 130 Opal fs Synchronously Pumped Optical Parametric Oscillator B-10...

  • Page 131: Stepper Calibration Procedure

    Appendix C Servo Wavelength Monitor Calibration Complete this calibration only when the actual wavelength differs from Caution! the displayed wavelength by more than ±3.0 nm after running Scan from the Setup menu. The latter is a day-to-day self-calibration Length routine, and we recommend you perform this routine each time you start up the Opal system.
  • Page 132 Opal fs Synchronously Pumped Optical Parametric Oscillator Use a monochromator to monitor the Signal wavelength and set its wavelength to the peak wavelength for the installed optic set (i.e., 1.300 µm or 1.500 µm). If necessary, adjust the Opal cavity length via the motor position con- trol in the Manual Control menu to set the Opal to 1.300 µm for the 1.3 µm set and 1.500 µm for the 1.5 µm set.

  • Page 133: Table C-1: 1St Order Settings For Several Opal Wavelengths

    Servo Wavelength Monitor Calibration 15. Press the key to exit the Manual Control menu. Back 16. From the Diagnostics menu, select Cal. Wavelng 17. Measure the actual operating wavelength of the Opal Signal output beam with the monochromator, then select the Set Actual Wavelength field and use the up/down push buttons to enter that measured value.
  • Page 134 Opal fs Synchronously Pumped Optical Parametric Oscillator...

  • Page 135: Appendix D: Replacing The Pcmcia Card Battery

    Appendix D Replacing the PCMCIA Card Battery The 512 kB memory card found in the controller uses a PCMCIA Opal small 3 V disk battery to maintain the data stored in it. The expected life- time of the battery is approximately 2–3 years, so it is prudent to change the battery every 2 years regardless of use.

  • Page 136: Procedure

    Opal fs Synchronously Pumped Optical Parametric Oscillator Epson One side white, opposite side light blue. Latch retains battery. Battery: CR2025 Epson One side green/brown/copper, opposite side brown. Latch retains battery. Battery: BR2325 Panasonic BN-512HMC Gray and green with gray edge trim. Screw retains battery. Battery: BR2325 Procedure...
  • Page 137 Replacing the PCMCIA Card Battery Observe the polarity of the battery as you remove it (it is possible to install the battery backwards in the Panasonic card). There is a “+” sign on the battery on its positive side (the side without the seam). The “+”...
  • Page 138 Opal fs Synchronously Pumped Optical Parametric Oscillator...

  • Page 139: Appendix E: Using The Optional Rs-232/Ieee-488 Interface

    Using the Optional Appendix E RS-232/IEEE-488 Interface This appendix explains how to operate the Opal system from a remote source using either the optional serial interface or the par- RS-232 IEEE-488 allel interface, the latter commonly referred to as the General Purpose Inter- face Bus, or .

  • Page 140: Format And Syntax Rules

    Opal fs Synchronously Pumped Optical Parametric Oscillator are sent from the terminal keyboard, and status responses are returned to the video monitor. A computer can also provide automatic control in addi- tion to interactive control, and it can use either interface. For automatic control, a program designed by the user and based on the command and queries listed in this appendix can be run on the computer to step the con- troller through a sequence of operations.
  • Page 141 Using the Optional RS-232/IEEE-488 Interface < > :SOURCE:WLEN:x.xxx —Set Wavelength Sets the desired signal wavelength in microns. The Opal will immediately begin moving toward the specified wavelength. Progress can be monitored with the :read:wlen? and ? commands. (This command is ignored if *STB the Opal is in wavenumber mode.) <...

  • Page 142: Additional Commands Required By The Ieee 488.2 Standard

    Opal fs Synchronously Pumped Optical Parametric Oscillator < > :SCANLENGTH —Run Scan Length Same as pushing "Scan Length" button from the Laser Setup menu. A suc- cessful scan results in the bits being set in the status LOOPON WLSET byte. During the "checking the calibration"...
  • Page 143 Using the Optional RS-232/IEEE-488 Interface EXEERR—Execution error The Opal could not execute the command. For example, it cannot recall a setup which does not exist, or go to an out-of-range wave- length. DEVERR—device error (always 0) QRYERR—query error (always 0) RQSCTNL—request control (always 0) OPCMPL—operation complete (set by *OPC) Bits in the...

  • Page 144: Connections

    Opal fs Synchronously Pumped Optical Parametric Oscillator < > *TST? —Self-Test Query Returns a “1” to indicate success. (It does not actually run any internal tests on the Opal.) < > *WAI —Wait-to-Continue Command This is a no-operation (no-op) command. It is used to add wait states between readings or between a command and a read.
  • Page 145 Notes Notes-1...
  • Page 146 Opal fs Synchronously Pumped Optical Parametric Oscillator Notes-2...
  • Page 147 Notes Notes-3...
  • Page 148 Opal fs Synchronously Pumped Optical Parametric Oscillator Notes-4...
  • Page 149 Notes Notes-5...
  • Page 150 Opal fs Synchronously Pumped Optical Parametric Oscillator Notes-6...
  • Page 151 Report Form for Problems and Solutions We have provided this form to encourage you to tell us about any difficulties you have experienced in using your Spectra-Physics instrument or its manual—problems that did not require a formal call or letter to our service department, but that you feel should be remedied. We are always interested in improving our products and manuals, and we appreciate all suggestions.

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