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Alpes Lasers QUANTUM CASCADE User Manual

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UANTUM
ASCADE
ASER
SER
S
ANUAL
Version number 3.1.8
c 2016 A
L
SA
LPES
ASERS

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  • Page 1 ’ UANTUM ASCADE ASER ANUAL Version number 3.1.8 c 2016 A LPES ASERS...
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  • Page 3 COPYRIGHT INFORMATION This manual can be copied and distributed under the following conditions: the work must be attributed in the manner specified by the author or licensor, and cannot be altered or transformed. WARRANTY 1. The customer must control the incoming deliveries and inform A LPES ASERS about incomplete shipments or defective goods within 30 days after delivery.
  • Page 4 DOCUMENT VERSION This is Version 3.1.8 of the manual, published on March 11th, 2016, superseding version 3.1.7 of the manual, published on October 16th, 2015. The following modifi- cations have been applied since the publication of version 3.0: Date of publication Version number Changes 11/3/2016...
  • Page 5 Preface This manual is a reference tool for personnel using A QCLs and elec- LPES ASERS tronic equipment. Its purpose is to provide the customer with sufficient information to carry out normal installation and operating procedures. It is not intended to replace or supersede any local directive.
  • Page 6 Typesetting conventions Table 2 gives a list of the acronyms used in this manual. A boxed item indicates a hardware setting on an electronic device.  $ %%   &   ' %  #   (   )* + ,  "-  "" $    ( $' * +     "  -&#  (  $  #  #  %%       #  &   %%   -   (  # ."  %        "   (  "     ...

  • Page 7: Table Of Contents

    Contents Preface 1. Overview 1.1. A products ......LPES ASERS 1.1.1. QCL parameters and performance ....1.1.2.
  • Page 8 3.3. Connections ....... . 3.3.1. LLH ....... . . 3.3.2.
  • Page 9 6. Technical specifications 7. Maintenance 7.1. Laser installation in LLH housing ..... 7.1.1. Handling ......7.1.2.
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  • Page 11: Overview

    LPES ASERS is given, as well as a brief introduction to the detection principle and fields of applica- tion of quantum cascade lasers (QCLs). Contents 1.1. A products ....

  • Page 12: Alpes Lasers Products

    Chapter 1: Overview 1.1. A products LPES ASERS manufactures two types of Quantum Cascade Lasers (QCLs): sin- LPES ASERS glemode Distributed-Feedback (DFB) or multimode Fabry-Perot (FP), which can be operated in two modes: continuous wave (CW) or pulsed. A lasers are...

  • Page 13: Qcl Mounting

    1.1 A products LPES ASERS figure 1.2. The surface of the ceramic pads is covered with a gold layer and their sides have a whitish ceramic color. The golden surface must be positioned upwards. When looking into the LLH from the top, the pad left of the direction of emission is labeled DN for down, and the right pad UP for up.

  • Page 14: Qcl Housings And Packages

    Chapter 1: Overview 1.2. QCL housings and packages QCLs can be delivered in 5 kinds of packages: LPES ASERS Chip-on-Carrier (CoC) A laser chip available on stock is mounted on either a NS or ST submount (see section 1.1.3) . These submounts can be integrated into a LLH or HHL housing, or can be sold separately, to be integrated in a piece of equipment manufactured by the customer.

  • Page 15: Laboratory Laser Housing (Llh)

    1.2 QCL housings and packages 1.2.1. Laboratory Laser Housing (LLH) The LLH consists of a housing unit that includes a TEC and encapsulates the QCL chip; it is designed to ease its installation and replacement. Its internal temperature is controlled by a Peltier junction and a PT-100 temperature sensor, and can reach tempuratures of less than -30 C.

  • Page 16: High Heat Load (Hhl) Housing

    Chapter 1: Overview 1.2.2. High Heat Load (HHL) Housing The HHL housing is much smaller than the LLH and is completely sealed. The HHL contains a Peltier junction and a PT-100 or NTC temperature sensor, which can be controlled by the TC-3 (see section 5.1) or a local temperature control system. Heat dissipation is performed by thermal contact with its copper base;...

  • Page 17: To3 Housing

    1.2 QCL housings and packages 1.2.3. TO3 Housing The TO3 housing is a hermetically sealed small-footprint housing designed to be in- tegrated into commercial devices. It is available in two versions: the TO3-W has a divergent output through an AR coated window, and the TO3-L (shown in figure 1.6) has a collimated output.

  • Page 18: Starter Kit

    Chapter 1: Overview 1.3. Starter kit The purpose of the Starter Kit is to readily operate an A QCL. The user LPES ASERS must provide an external power supply; see section 3.1 for prerequisites and section 1.4 for recommended peripherals. The kit includes all the necessary cables for the LLH or HHL housing, electronic devices (TCU or TC-3, LDD and TPG for pulsed operation), power cables and connections for optional water cooling.
  • Page 19 1.3 Starter kit Pulsed mode The Starter Kit shown in figure 1.8 is meant to operate QCLs in pulsed mode. It consists of the following elements, which are described in dedicated subsections: Temperature Controller Unit (TCU), section 1.3.1 or TC-3 Temperature Con- troller, section 1.3.2.

  • Page 20: Temperature Controller (Tcu)

    Chapter 1: Overview 1.3.1. Temperature Controller (TCU) CAUTION: The TCU unit was sold from 1998 until 2012. It was sold in two different models, TCU151 and TCU200, with identical functionalities and controls. It was superseded starting in 2013 with the TC-3 unit described in §...

  • Page 21: Temperature Controller (Tc-3)

    1.3 Starter kit 1.3.2. Temperature Controller (TC-3) The TC-3 purpose is to control the laser temperature inside the LLH or HHL housing. It powers the Peltier junction and reads the temperature from the PT100 sensor coupled to the laser chip (see section 1.2.1). The TC-3 software is set at the factory to work with your instrument if it was bought as a Kit.

  • Page 22: Laser Diode Driver (Ldd)

    Chapter 1: Overview 1.3.3. Laser Diode Driver (LDD) CAUTION: The LDD and TPG units are legacy units that are being phased out as of 2015 in favour of the S-2 QCL Pulser described in § 1.3.5. The Laser Diode Driver shown in figure 1.11 is a switching unit that creates cur- rent pulses to drive the laser.
  • Page 23 1.3 Starter kit Note: the exact measurement of short strong pulses with diodes and averaging circuitry is non-trivial, therefore accurate time and voltage measurements should be performed directly on the LLH or HHL housing through the laser and base connec- tors.

  • Page 24: Ttl Pulse Generator (Tpg)

    Chapter 1: Overview 1.3.4. TTL Pulse Generator (TPG) The TPG shown in figure 1.12 is designed to power and control the LDD (see section 1.3.3) by generating TTL pulses on 50 Ω . The pulse duration can be set from 0 to µ...

  • Page 25: Peripherals

    LPES ASERS lasers. CW laser driver : precision laser diode current source such as ILX L LDX-3232 High Compliance Quantum Cascade Laser IGHTWAVE Diode Driver http://www.ilxlightwave.com/propgs/laser-diode-driver-3232.html Note: cables compatible with the LLH or HHL housing can be provided by LPES...

  • Page 26: Fields Of Applications

    Chapter 1: Overview 1.5. Fields of applications 1.5.1. IR The A QCLs address the need for gas sensing and spectroscopy ap- LPES ASERS µ plications in the wavelength region from 3 to 15 m; most chemical compounds have their fundamental vibrational modes in the mid-infrared. More specifically, the high transparency of the atmosphere in two so-called atmospheric windows at approxi- mately 3-5 µ...

  • Page 27: Thz

    1.5 Fields of applications 1.5.2. THz Terahertz radiation is safe and non-ionizing. It bridges the gap between the mid- infrared and microwaves. It can penetrate most non-conductive materials and can be used in a wide range of applications: Water content mapping Tissue density mapping Metal detection Spectral identification...
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  • Page 29: Safety

    2. Safety electronic equipment operates at high voltages and includes a L LPES ASERS ASER that may cause serious injury if not handled properly. The guidelines in this document follow as closely as possible the IEC 60825-1 International Standard for safety of laser products.

  • Page 30: General Safety Considerations

    Chapter 2: Safety 2.1. General safety considerations If any of the following conditions exist, or are suspected, do not use the instrument until safe operation can be verified by trained service personnel: Visible damage Severe transport stress Prolonged storage under adverse conditions Failure to perform intended measurements or functions If necessary, return the instrument to A for service or repair to ensure...

  • Page 31: Notation

    2.2 Notation 2.2. Notation The use of DANGER, WARNING and CAUTION notation in this manual is in compli- ance with the SEMI standard S-13-0298 ; their definition is given below. They may also be used to alert against unsafe practices. DANGER: Indicates an immediate hazardous situation, which, if not avoided, may result in death or serious injury.

  • Page 32: Symbols And Labels

    Chapter 2: Safety 2.2.1. Symbols and labels The danger and warning symbols used in this manual are shown in table 2.1. general danger electrical hazard radiation hazard safety eyewear mandatory ASER Table 2.1.: Safety symbols most commonly used in the A user’s manual.

  • Page 33: Health Hazard

    2.3 Health hazard 2.3. Health hazard There are three main sources of hazard associated with the Starter Kit: radiation, detailed in section 2.3.1; ASER electrical, detailed in section 2.3.2; environmental, detailed in section 2.3.3. 2.3.1. L radiation hazard ASER The eyes and skin are the body parts the most likely to be injured. Warnings for tasks that may potentially adversely affect the health of the operator of a QCL are shown below.
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  • Page 35: Installation

    3. Installation This chapter presents the general workflow between delivery and operation of A LPES QCLs and electronic equipment: ASERS IMPORTANT: The facility must fulfill all prerequisites listed in section 3.1, all utilities must be duly prepared in a suitable location. The location of A QCLs and electronic LPES ASERS...

  • Page 36: Prerequisites

    Chapter 3: Installation 3.1. Prerequisites This section describes the environmental conditions in which A QCLs LPES ASERS and other electronic equipment should be stored, handled and the prerequisites for its operation. The items listed in table 3.1 must be provided by the customer for A LPES QCLs and electronic equipment to be operated.
  • Page 37 3.1 Prerequisites Storage All A lasers are delivered in a hermetic waterproof storage box, shown LPES ASERS in figure 3.1, in which the laser chip is held with pins. This box should always be used when storing the laser out of its housing. The laser chip is soldered to the pads using In soldering, which melts at 120 C, therefore the storage temperature should not exceed 80 C.

  • Page 38: Cooling

    Chapter 3: Installation 3.1.2. Cooling The laser’s performance is highly dependent on its operating temperature, it is there- fore necessary to cool down the laser accordingly. The following setups can be used: for LLH only: closed loop cooling system with chiller for LLH only: tap water, Swagelok fitting to the tap, 4 mm tubing good mechanical contact between the LLH or HHL housing or QCL submount and the heat sink, such as an optical table...

  • Page 39: Receiving Procedure

    3.2 Receiving procedure 3.2. Receiving procedure Upon delivery of the Starter Kit, the following procedure must be performed: 1. check that all of the components are included in the shipment. By default, the QCL is included in its housing ; the remainder consists of different sets of com- ponents depending on the housing and operation mode of the laser.
  • Page 40 Chapter 3: Installation USE ONL YWITH250V FUSES / EMPLOYER UNIQUEMENT AVEC DES FUSIBLES DE 250v 110− 120V Figure 3.2.: TCU installation: rear panel (left), fuse holder (right). QCL user’s manual v3.1.8...

  • Page 41: Connections

    3.3 Connections 3.3. Connections Table 3.2 lists the cables and use of all connections for the Starter Kit including the LLH or HHL housing operated in pulsed or CW mode. Refer to figure 3.3 for cable identification. Table 3.2.: Starter Kit connections. The "ref" column refers to cable numbering in figure 3.3.
  • Page 42 Chapter 3: Installation Figure 3.3.: Starter Kit cables. QCL user’s manual v3.1.8...

  • Page 43: Llh

    3.3 Connections 3.3.1. LLH The LLH front and rear panels shown in figure 3.4 consist of the following items: anti-reflective (3.5 to 12 µ m) ZnSe coated laser beam window (1) CTL cable connector (2) for Peltier junction and PT-100 sensor connector for LBI or CIL cable (3) cooling water flow fittings (4) for 4 mm flexible cables monitoring base connector (5) and laser connector (6) for direct voltage mea-...

  • Page 44: Hhl

    Chapter 3: Installation 3.3.2. HHL The HHL housing and CTLm cable shown in figure 3.5 must be connected according to the numbering of the CTLm connector pins (from 1 to 10) and the HHL connector pins description provided in section 3.3.6. If you use a TC-3 temperature controller, you should use the TC-HHL cable instead, with an identical connector on the HHL side.

  • Page 45: To3

    3.3 Connections 3.3.3. TO3 Figure 3.6 shows the TO3 housing connector; the pinout is detailed in table 3.3. TO3- L and TO3-W housing have identical pinouts. The polarity of the laser connection is specified on the laser datasheet. Figure 3.6.: TO3 housing connector. Pin nb Purpose TEC +...

  • Page 46: Ldd

    Chapter 3: Installation 3.3.4. LDD Figure 3.7 show the LDD connectors. The low-impedance line LBI has a locating pin to avoid false connection on the LLH laser housing and on LDD. The LBI has to be connected with "NEG" up unless specifically told to connect with "POS" up. Figure 3.7.: LDD low impedance connector for LBI cable (1), drive cable connector for CPL cable (2) and monitoring BNC connector (3).

  • Page 47: Ctl Cable

    3.3 Connections 3.3.5. CTL cable The TCU controls the temperature of the LLH with a Peltier junction and monitors the temperature with a PT100 through the CTL cable. The Peltier connector shown in figure 3.8 carries 6 pins, described in table 3.4. Pin 1 is circled, and a half-moon engraving runs from pin 1 to pin 6.

  • Page 48: Ctlm Cable

    Chapter 3: Installation 3.3.6. CTLm cable The CTLm cable connects the HHL on one side, and splits into two connectors on the other side: one for the TCU, the other for the laser driver. The TCU controls the temperature of the HHL with a Peltier junction and monitors the temperature with a PT100 temperature sensor.

  • Page 49: Tc-Llh Cable

    3.3 Connections 3.3.7. TC-LLH cable The TC-3 controls the temperature of the LLH with a Peltier junction and monitors the temperature with a PT100 through the TC-LLH cable. The Peltier connector is identical to the connector shown in the left side of Fig. 3.8. The controller connector is a DB-15 connector described in Table 3.6.
  • Page 50 Chapter 3: Installation Figure 3.9.: CPL cable. Figure 3.10.: DE-9 connector pinout numbering. pin nb purpose + external power supply (red banana cable) center of LEMO connector (+12 V) (not connected) center of BNC connector + yellow banana cable - external power supply (black banana cable, associated with red banana cable) LEMO ground (chassis) BNC ground (chassis) - black banana cable (associated with yellow banana cable)

  • Page 51: Cil Cable

    3.3 Connections 3.3.10. CIL cable The CIL cable connects the LLH housing to the ILX LDX-3232 CW laser driver. On the LLH end, the connector consists of two rows of pin slots. All slots of one row are connected together, resulting in two terminals. In order to insure the correct po- larity, some slots are filled with solder, which should match broken pins on the LLH connector.

  • Page 52: Connection Procedure

    Chapter 3: Installation 3.3.11. Connection procedure The procedure to connect the Starter Kit components depends on the laser housing and operation mode. Refer to figure 3.3 for cable identification. In all cases To prevent any damage to the Starter Kit components, make sure the TPG, TCU, TC-3 and the external power supply are all turned off.
  • Page 53 3.3 Connections Pulsed mode operation Note: This section describes the procedure to be used using a Starter Kit based on the combination of the TPG pulser and LDD driver. If you use a S-2 QCL Pulser, refer instead to § 5.4. 1.
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  • Page 55: Qcl Operation

    4. QCL Operation In this chapter, the general operation principle of a QCL is presented, and its main characteristics are illustrated using actual plots included in the datasheet provided with each A QCL upon delivery. LPES ASERS Contents 4.1. Principle of operation ..... . 46 4.2.

  • Page 56: Principle Of Operation

    Chapter 4: QCL Operation 4.1. Principle of operation Quantum Cascade Lasers (QCLs) are unipolar lasers emitting in the mid-infrared from 4 to 20 microns. The laser is a ridge of InGaAs and AlInAs grown on InP providing gain and a Fabry-Pérot cavity in order to build up the laser oscillations. A...

  • Page 57: Lpes Asers Datasheet

    4.2 A datasheet LPES ASERS 4.2. A datasheet LPES ASERS The datasheet provided with each A QCL upon contains the data ob- LPES ASERS tained from standardized quality control tests performed at A production LPES ASERS site. The tests are performed on the QCL installed in a test-bench LLH housing oper- ated at a temperature ranging from -30 C up to their maximal operating temperature (up to +50 C).

  • Page 58: Alpes Lasers

    Chapter 4: QCL Operation 4.3. QCL spectra A QCL is characterized by its emission frequency (spectral domain), wavelength or wavenumber (spatial domain); all three are equivalent. The following table gives typi- cal values for A QCLs. LPES ASERS wavelength ( λ...
  • Page 59 4.3 QCL spectra Figure 4.1.: Spectra of a DFB laser operated in CW mode (top) and pulsed mode (bottom) with different currents and temperatures. c 2016...
  • Page 60 Chapter 4: QCL Operation Figure 4.2.: Spectra of a FP laser operated in CW mode at fixed temperature and different currents. Figure 4.3.: Spectra of four different broadgain lasers. QCL user’s manual v3.1.8...

  • Page 61: Linewidth Of Pulsed Single-Mode Dfb Qcls

    4.3 QCL spectra 4.3.2. Linewidth of pulsed single-mode DFB QCLs The linewidth of DFB QCLs operated in pulsed mode depend on the pulse length and is affected by chirping. Chirping occurs because of thermal variations of the laser. Fine linewidths are obtained with short pulses (25 to 50 ns). A LPES ASERS QCLs are tested using pulse length of 25 to 50 ns, showing a linewidth <...

  • Page 62: Bandwidth Of Multi-Mode Fp Qcls

    Chapter 4: QCL Operation IMPORTANT: QCLs operated in CW mode are guaranteed to be single mode if LPES ASERS operated with long pulses (> 10 ms) only. 4.3.4. Bandwidth of multi-mode FP QCLs In the case of FP QCLs, the bandwidth is defined as the wavelength range in which 99% of the power is emitted.
  • Page 63 4.4 I-V curve and emitted power Figure 4.4.: IV curves of DFB laser (top) and FP laser (bottom) operated in CW mode at different temperatures. c 2016...

  • Page 64: Maximum Operating Current

    Chapter 4: QCL Operation 4.4.1. Maximum operating current All QCLs have a maximum operating current above which a Negative Differential Re- sistance (NDR) appears and may destroy the laser. As an example, figure 4.5 shows the IV curve and emitted power of a DFB QCL operated in pulsed mode: the green squares indicate the maximum current for monomode operation, 4.7 A from -30 to 30 C in the present case.

  • Page 65: Maximum Ldd Voltage

    4.4 I-V curve and emitted power 4.4.2. Maximum LDD voltage Figure 4.6 shows the pulse peak current and emitted power as a function of the volt- age fed to the LDD. When the LDD is used to operate a laser in pulsed mode, the QCL operating current is controlled by the LDD, which is itself controlled by changing its operating voltage.

  • Page 66: Other Dfb Qcl Plots

    Chapter 4: QCL Operation 4.4.3. Other DFB QCL plots The plots displayed in figure 4.7 show the emitted power and LDD voltage as a func- tion of frequency, temperature and operating current. These curves help when setting up the operation parameters of a DFB QCL. Figure 4.7.: Emitted power (top) and LDD voltage (bottom) as a function of frequency for a DFB laser operated in pulsed mode at different temperatures.

  • Page 67: Beam Properties

    4.5 Beam Properties 4.5. Beam Properties Divergence Figure 4.8 shows a typical A QCL beam profile. Unipolar lasers consist LPES ASERS of tightly confined waveguides; for this reason, the beam diffracts strongly at the output facet and has a full divergence angle of about 60 degrees perpendicular to the layer (vertical angle) and 40 degrees parallel to the layers (horizontal angle).
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  • Page 69: Starter Kit Operation

    5. Starter Kit Operation In this chapter are presented the operation instructions for the different components of the Starter Kit and the procedures to be followed for starting up and operating an laser. LPES ASERS IMPORTANT: The operating parameters are listed in the datasheet provided with each laser;...

  • Page 70: Temperature Controller

    Chapter 5: Starter Kit Operation 5.1. Temperature Controller TC-3 The TC-3 has its own complete manual. This section outlines a quick start-up and instructions for use with the A housings. A more complete manual is LPES ASERS available on the A website: LPES ASERS...
  • Page 71 5.1 Temperature Controller TC-3 Make the same adjustments to the high and low temperature limits (T-High Lim and T-Low Lim), as appropriate for your application. These values should not exceed those stated in the datasheets of the laser used. Next you will need to adjust the constants to reflect the values for your temperature sensor as shown in table 5.2.
  • Page 72 Table 5.3.: Recommended temperature change rates CAUTION: The TC-3 contains a feature known as AutoTune. Usage of this feature is NOT RECOMMENDED with the housings of Alpes Lasers. Using AutoTune risks damaging or reducing the lifetime of the Peltier elements.

  • Page 73: Temperature Controller Unit (Tcu)

    5.2 Temperature Controller Unit (TCU) 5.2. Temperature Controller Unit (TCU) The TCU front and rear panels are shown in figure 5.2 and described below. Figure 5.2.: TCU front (left) and rear (right) panels. c 2016...
  • Page 74 Chapter 5: Starter Kit Operation Command description (1) Set Temperature 5 turns knob: Allows to set the internal temperature refer- ence. (2) LCD 3 digits display: Used to display either the actual sensor or reference temperature/current. (3) Switch to select which temperature or current signals to display. (4) Alarm display LED.

  • Page 75: Tcu Startup

    5.2 Temperature Controller Unit (TCU) 5.2.1. TCU startup 1. make sure the laser power supply is disconnected (see section 3.3 for connec- tions) 2. turn on the TCU 3. set the desired temperature: a) select Setting oC using the switch (3) shown in figure 5.2 to display the desired temperature b) turn the knob (5) to set the temperature to the desired value c) select Real oC using the switch (3) to display the actual temperature...

  • Page 76: Tcu Interlock

    Chapter 5: Starter Kit Operation 5.2.3. TCU interlock The built-in TCU interlock is activated when a fault occurs within the TCU controller, e.g. prompt temperature rise. The interlock is by default an NC (Normally Close) relay contact and may be reset by pressing the reset button (3) shown in figure 5.3. Note: it is also possible to set the Interlock as a NO (Normally Open) contact.

  • Page 77: Ttl Pulse Generator (Tpg)

    5.3 TTL Pulse Generator (TPG) 5.3. TTL Pulse Generator (TPG) The front and rear panels of the TPG are shown in figure 1.12; a detailed view of the front panel is shown below in figure 5.4. Figure 5.4.: TPG front panel. Command description The pulse duration can be set from 0 to 200ns and the interval between pulses from µ...

  • Page 78: Internal And External Modes

    Chapter 5: Starter Kit Operation 5.3.1. Internal and external modes The TPG can be operated in internal or external mode; the mode is selected with a switch on the rear panel of the TPG, as shown in figure 1.12. The input and output signals are provided or generated through the four BNC connectors shown in figure 5.4: In internal mode, a periodic signal is generated through the Output BNC con-...
  • Page 79 5.3 TTL Pulse Generator (TPG) Figure 5.6.: TPG Trig IN external mode signal. c 2016...

  • Page 80: Setting The Pulse Parameters

    Chapter 5: Starter Kit Operation 5.3.2. Setting the pulse parameters 1. remove the TPG from the Starter Kit and connect it to the mains independently 2. set the TPG mode to internal 3. connect the TPG to a scope using the Output BNC cable: a 5V TTL signal should be displayed 4.

  • Page 81: Maximum Duty Cycle

    5.3 TTL Pulse Generator (TPG) 5.3.3. Maximum duty cycle The TPG is capable of operating with pulses as long as 200 ns; however for short periods (high duty cycle) the following limitations apply: T=400ns: ............t max = 200ns T=300ns: .

  • Page 82: Pulser (S-2)

    Chapter 5: Starter Kit Operation 5.4. S-2 Pulser (S-2) Figure 5.7.: S-2 OEM configuration with HHL. The S-2 pulser provides short electrical pulses to the laser. It connects directly to the laser in an HHL housing with pins as shown in table 3.5; adapter cables are available for other types of housing.

  • Page 83: Internal Control

    5.4 S-2 Pulser (S-2) Figure 5.8.: S-2 back pin-out. The position of pin 1 is marked by a triangle on the top of the connector. TEC Input (+) Temperature Sensor (+) RS232 Rx Interlock (short with pin 14 to enable laser Ground Power Supply Input , 9-24 V RS232 Tx...
  • Page 84 Chapter 5: Starter Kit Operation Figure 5.9.: STC-3 cable. QCL user’s manual v3.1.8...
  • Page 85 5.4 S-2 Pulser (S-2) Figure 5.10.: Dialog Box for internal control. age current of 2.5 A. The maximum peak current as function of duty cycle and pulse repetition rate is shown in Fig. 5.11. The maximum allowed peak current for the cur- rent duty cycle and repetition rate is displayed in the graphical user interface.

  • Page 86: External Control

    Fig. 5.12 show all possible commands accepted by the S-2 pulser arranged in a python example. Alpes Lasers offers these commands for convenience only. Software support will not be provided after delivery. 5.4.2. External Control In external control, the pulses are triggered using the External Modulation Input signal.
  • Page 87 5.4 S-2 Pulser (S-2) WARNING: Internal pulses must be disabled during external control and vice-versa. Enabling internal and external pulses simultaneously might result in damages to the laser and the pulser. from s2 import serial_open, serial_close, s2_serial_setup, S2_settings, S2_info, s2_set_settings, s2_query_settings, s2_query_info, S2_PULSING_INTERNAL port = serial_open(’/dev/tty.usbserial-FTXIRYHE’) s2_serial_setup(port)

  • Page 88: General Procedures

    Chapter 5: Starter Kit Operation 5.5. General procedures CAUTION: The laser shall only be operated under conditions as specified in the datasheet or by A directly: all other operation may LPES ASERS result in the destruction of the laser and loss of warranty. 5.5.1.
  • Page 89 5.5 General procedures vi. connect the red/black banana cables vii. switch on the external power supply b) setup the TPG pulse parameters following the guidelines of section 5.3 c) connect the TPG back to the Starter Kit and turn it on CAUTION: Make sure the laser temperature is below specifications before turning on the external power supply.
  • Page 90 Chapter 5: Starter Kit Operation b) reset it to 0 c) align the laser beam with the powermeter The power should start rising around the threshold of the A datasheet LPES ASERS IV curve (see section 4.4). Note: exact power measurement of an IR beam is very difficult to predict as it depends on the room temperature and powermeter characteristics.

  • Page 91: Qcl Shutdown

    5.5 General procedures 5.5.2. QCL shutdown 1. reduce the external power supply voltage slowly, do not reach 0 as the polarity might reverse CAUTION: Make sure the polarity of the laser is correct. Permanent damage may occur. 2. if a pulsed QCL is operated with TPG and LDD: turn off the TPG first 3.
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  • Page 93 6. Technical specifications The technical specifications of A products are given in the following LPES ASERS tables: QCLs in table 6.1 housings in table 6.2 electronic equipment in table 6.3 Broadgain Lasers bandwidth in table 6.5 Some technicals drawings are provided in figures 6.6, 6.7, 6.8 and 6.9. !"#$%"&'$()*+(()&,-.
  • Page 94                ! "# $% & ' #( )# ))() '*               +, %%-+%%-  .%% %% %% ) %% ./#%% (0' ./#%% (0' ./#%% (0' ./#%% (0'  %1)() %1)() %## &# )() ## (-(1&%45 (- ## (2 -(1&%4 2 ...
  • Page 95        4#  4#    5)655072(80/5      !"#$ 59&/ % "):/:):/50/ %  8 ;2 &' () %/((8<() /)/ ()% ((8)/=>2 ?-//  ,2 ' /5 @:$!-/- A2 /5 &  6/0 ?? B"# & / A727/ *+ A727/ + % %...
  • Page 96 Chapter 6: Technical specifications Figure 6.4.: Technical specifications of A electronic equipment (contin- LPES ASERS ued from 6.3) QCL user’s manual v3.1.8...
  • Page 97                                  Figure 6.5.: Examples of broadgain laser parameters, where FP min and max are the limits of the multimode emission, PEC min and max are the observed limits of single mode pulsed emission in an external cavity and CWEC min and max the observed limits of continuous emission in an external cavity.
  • Page 98 Chapter 6: Technical specifications Figure 6.7.: NS (left) and ST (right) mounting support. front view top view (values in mm) emission from front facet Figure 6.8.: NS mounting. QCL user’s manual v3.1.8...
  • Page 99 0.6mm pad front view copper submount 20mm "down" "up" top view laser chip emission from front facet Figure 6.9.: ST mounting. c 2016...
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  • Page 101 7. Maintenance This chapter explains the maintenance procedures for the installation of a QCL in the HHL housing and Starter Kit components calibration. IMPORTANT: The maintenance procedures included in this chapter have to be followed carefully by expert users only. Delicate operations may result in permanent damage to the laser if not carried out properly.

  • Page 102: Laser Installation In Llh Housing

    Chapter 7: Maintenance 7.1. Laser installation in LLH housing The guidelines for manipulating the laser safely and the procedure for exchanging the laser in a LLH housing are outlined in this section. 7.1.1. Handling The laser should always lay flat, with its vertical axis upwards, on a flat and stable sur- faces.

  • Page 103: Contact Set

    7.1 Laser installation in LLH housing CAUTION: Do not touch the bonds nor the laser chip itself, as the QCL may be permanently damaged. CAUTION: Avoid any dust to deposit on the laser chip or any laser submount item. Malfunctioning or permanent damage to the laser may occur. 7.1.2.
  • Page 104 Chapter 7: Maintenance Figure 7.3.: Schematic side view of the laser submount, contact set and LLH. Figure 7.4.: Inside view of the LLH, without (left) and with (right) contact set. QCL user’s manual v3.1.8...

  • Page 105: Procedure

    7.1 Laser installation in LLH housing 7.1.3. Procedure This procedure allows the installation of a new laser into the LLH housing. 1. disconnect the LLH and open its cover (2), as shown in figure 7.7 Figure 7.5.: Exchanging the laser in the LLH housing. 2.
  • Page 106 Chapter 7: Maintenance Figure 7.6.: Laser exchange procedure: removing the contact set (left), securing the laser submount (right). CAUTION: Do not drop the screws onto the submount. This may result in permanent damage to the laser. 6. secure the laser submount into the LLH with the two dedicated screws; use tweezers to hold the screw in place while screwing with an allen wrench.

  • Page 107: Up And Dn Contact Exchange

    7.1 Laser installation in LLH housing 7.1.4. UP and DN contact exchange Follow procedure 7.1.3, adding those additional steps to step 7: 1. remove the screw (5) located at the back of the contact set, as shown in figure 2. remove the copper contact (6) 3.

  • Page 108: Calibration Procedures

    Chapter 7: Maintenance 7.2. Calibration procedures In this section the calibration procedures for the TPG and TCU are detailed. In both cases a few preliminary steps must be followed: 1. Switch off the device. 2. remove the TPG or TCU cover (refer to figure 7.8): a) Pull off the light gray plastic pieces of the side of the front and back plates.

  • Page 109: Tcu Interlock Level Setting Procedure

    7.2 Calibration procedures 7.2.1. TCU interlock level setting procedure This procedure allows to set the TCU interlock level. 1. switch off the TCU 2. unplug the power cable 3. remove the cover to access the main board following step 2 of the previous procedure.

  • Page 110: Tcu Calibration

    Chapter 7: Maintenance 7.2.2. TCU calibration This procedure must be followed for a general calibration of the TCU command knobs and selectors. Refer to section 5.2 for TCU front panel commands description. IMPORTANT: The TCU is calibrated in factory. This procedure is not a routine procedure and must be performed by experts only.
  • Page 111 7.2 Calibration procedures 3. +5V/-5V power supply check. CAUTION: Do not connect the signal IN-34 V DC (connector J1 (3)). This may result in permanent damage to the Peltier junction. a) Check that the input impedance between +5V/-5V and GND have the fol- lowing values: TP1 (4) - GND (5): >...
  • Page 112 Chapter 7: Maintenance 4. Sensing level and range adjustement (refer to figure 7.11) a) Replace the cable connected to J8 (4) with the 100 1 Ω resistor. Note: the precision (gold band on the resistor) is important. Connect one side of the resistor to pins 1 and 2, the other side to pins 3 and 4.
  • Page 113 7.2 Calibration procedures 5. Temperature Reference offset adjustment (refer to figure 7.12) a) Adjust B13 (3) to 0.000 with P3 (4) b) Set the temperature with the Set Temperature knob (Fig.40 (7)) to +5 C The temperature reference signal B13 should be 4.3V c) Set the temperature with the Set Temperature knob (Fig.40 (7)) to -5 C The temperature reference signal B3 should be...
  • Page 114 Chapter 7: Maintenance 6. Oscillator check (refer to figure 7.13): measure the frequency on the pin 7 of U13 (1); the value must be 28KHz + /- 3KHz. 7. Current/Voltage ratio adjustment (refer to figure 7.13) a) Adjust the trimmer P4 (6) in order to read B4 = 0.6V (4). b) Set the selector (5) to mode Setting +I: the LCD screen should display 1.00 A.
  • Page 115 7.2 Calibration procedures IMPORTANT: For the remainder of this procedure, limit the positive current to 1 A and the negative current to 1.2 A using the 5 turns knob. 8. Temperature limit threshold a) Measure the voltage on pin 2 of U10 (1): the value should be: 0.7V (= 70 C) (If needed, adjust it with the trimmer P9(2)).
  • Page 116 Chapter 7: Maintenance Figure 7.14.: TCU main board (zoom III and IV). QCL user’s manual v3.1.8...
  • Page 117 7.2 Calibration procedures 10. Current adjustment a) Set the selector (3) to Setting C and adjust the temperature value to 25 C by means of the Set Temperature 5 tuns potentiometer P8 (2). b) On the external power supply, rise slowly the voltage to 30 V and the cur- rent to 1.5 A: the tension should stabilize at 30 V.
  • Page 118 Chapter 7: Maintenance 11. Temperature limit testing a) Decrease the temperature limit threshold from 0.7 V to 0.3 V. For more details, see Temperature limit threshold on page 105. b) Increase the temperature reference to 35 C. When the threshold is overpassed, the red LED (1) in front panel should light up.

  • Page 119: Tpg Calibration

    7.2 Calibration procedures 7.2.3. TPG calibration These procedures describe the steps necessary to calibrate the TPG front panel knobs settings. Refer to figure 5.3 for the TPG commands description. IMPORTANT: The TPG is calibrated in factory. This procedure is not a routine procedure and must be performed by experts only.
  • Page 120 Chapter 7: Maintenance Figure 7.16.: TPG main board (view I). QCL user’s manual v3.1.8...
  • Page 121 7.2 Calibration procedures µ µ [5] Select the range 5 s to 105 s on the period selection knob. Turn the 10 turns adjustment knob to its last position. Adjust the adjustable capacitor max µ s adj (4) in order to obtain a 105 µ...
  • Page 122 Chapter : Maintenance Ω [12] Connect oscilloscope to the Output connector. Load with a 50 . Choose µ a repetition period of about 5 [13] Turn the boxduration adjustment knob to its last position. Adjust the Max duration capacitor (2) so it has an output pulse of 200 ns +/-5 ns. [14] Turn the boxduration adjustment knob to its first position.
  • Page 123 A. QCL theory and application notes A.1. QCL wavelength range Unlike standard bipolar semiconductor lasers (e.g. 1.55 µ m telecom devices), for which the emission wavelength is closely related to the band gap energy, the QCL transition consists in the transition of an electron inside sub-bands, from one upper quantum well level to a lower quantum well level.
  • Page 124 Chapter A: QCL theory and application notes A.2. QCL electrical response The QCL can be modeled with a combination of one resistor and two capacitors. R1 increases from a higher resistance at low biases to 1-4 Ohms at the operating point. Ω...
  • Page 125 B. Operations for advanced users In this section, tips for advanced users are provided for specific application. It is not recommended to perform these procedures under normal operation conditions. IMPORTANT: The operation instructions contained in this section must be performed by expert users only, as permanent damage to the laser may occur if not manipulated correctly.
  • Page 126 Chapter B: Operations for advanced users B.2. Soldering wire bonds from laser chip to submount IMPORTANT: Soldering bonds to the carrier is a delicate operation. Contact before attempting this operation. LPES ASERS As the QCL chip itself is soldered and the contact pads on the ceramics are made out of gold, it is not possible to use a normal Lead-Tin solder.
  • Page 127 0.6V to start bias current. The input stage has a voltage limit of 2.6V. The laser itself may be destroyed at lower bias-T control voltage; therefore the maximum rating has to be agreed with Alpes Lasers SA. the laser should be operated initially at lowest possible temperature Since a bias-T only allows to heat the laser.
  • Page 128 Chapter B: Operations for advanced users with increased bias current due to the additional heat. This reduces the number of lasers available for reaching a given emission wavelength. CAUTION: Applying a high bias current may destroy the laser due to thermal roll-over.
  • Page 129 B.3 Bias-T circuit for pulsed lasers Procedure 1. set the temperature to 15 C so that any moisture inside the package does not condense on the laser chip 2. Use current settings as indicated in the A datasheet LPES ASERS 3.
  • Page 130 Chapter B: Operations for advanced users B.4. CW modulation To operate a laser in CW mode, an AC signal is added to the DC current. It is recom- mended to modulate the external power supply directly, within the parameter range specified in the A datasheet.
  • Page 131 B.4 CW modulation (~ 1-2 Ohm) Figure B.3.: RLC circuit for external power supply protection. In general, is of the order of 1..2 Ω . For a modulation frequency of 10kHz, should therefore be of the order of 3mH or larger. rules of thumb for R and C To prevent the AC source from dominating or reverse biasing the current through the <...
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  • Page 133 C. Cryogenic operation of QCLs Alpes Lasers can deliver lasers with cooling solutions that can reach cryogenic tem- puratures. C.1. LN2 Dewar The LN2 Dewar is a modified Kadel dewar that serves as housing for a QCL. As it lacks a temperature control, it is typically used for lasers which do not tune appreciably with temperature, such as THz lasers or other Fabry-Perot lasers.
  • Page 134 C.1.2. Maintenance The laser sits in a vacuum. Over the course of normal operation the housing is air- tight. In case of a leak, the dewar can be sent back to Alpes Lasers to be re-sealed. C.2. Others Two other cryostats are offered by Alpes Lasers; a LN2/liquid helium cryostat and a Stirling cooler.

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