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Toptica Digilock 110 Manual

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Digilock 110
Feedback
Controlyzer
Manual: M-031 Version 09
Copyright
T
OPTICA
Lochhamer Schlag 19
D-82166 Graefelfing/Munich
Tel.: +49 89 85837-0
Fax: +49 89 85837-200
email: info@toptica.com
http://www.toptica.com
(December 2017 Subject to change without notice)
Manual
2017 T
Photonics AG
OPTICA
Photonics AG

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  • Page 1 Digilock 110 Feedback Controlyzer Manual Manual: M-031 Version 09  Copyright 2017 T Photonics AG OPTICA Photonics AG OPTICA Lochhamer Schlag 19 D-82166 Graefelfing/Munich Tel.: +49 89 85837-0 Fax: +49 89 85837-200 email: info@toptica.com http://www.toptica.com (December 2017 Subject to change without notice)
  • Page 3 We will provide you with quick and competent help through our service staff and product managers. You can contact us in the following ways: - Internet: service.toptica.com. In our support section you can find a list of frequently asked ques- tions and a service contact form - Email: service@toptica.com...

  • Page 5: Table Of Contents

    Scope 8.3.2 AutoLock 8.3.3 Spectrum Status Display Notes on Feedback Control Loops with the DigiLock 110 Signal to Noise and Bandwidth Considerations Frequency Modulation Techniques Controller Parameter Adjustment and Optimization Identification of Signal Polarity and Slope Relock Feature Signal Limitations in Analyzing the Locking Performance...
  • Page 6 11.3.2 Plug-On Board 11.4 Specifications of DigiLock 110 Connections 11.5 Directories of the DigiLock 110 Software 11.6 Pin Assignment of the DigiLock 110 Backplane 11.7 Declaration of CE Conformity 11.8 EU Legislation for Electrical and Electronic Equipment (EEE) 12 Guarantee and Service...

  • Page 7: The Feedback Controlyzer Digilock 110

    So far the different schemes require a corresponding set of adapted electronics. The DigiLock 110 integrates fast analog and digital electronics into a versatile general purpose locking module. Its up-to-date digital hardware allows to implement the scan generator, PID controllers and optional frequency modulation techniques all into one plug in module.

  • Page 8: Design And Operating Principle Of The Digilock 110

    Feedback Controlyzer DigiLock 110 Design and Operating Principle of the DigiLock 110 Figure 1 Schematic block diagram of the DigiLock 110 module For details of backplane connections see Figure 3 Page 4 Status: 5.12.17...
  • Page 9 1. The Feedback Controlyzer DigiLock 110 Figure 2 Schematic block diagram of the DigiLock 110 functional units and their Interaction Figure 3 Schematic block diagram of the connections to the DC 110 backplane Page 5 Status: 5.12.17...

  • Page 10: Safety Instructions And Warnings

    In addition, a NOTE ! heading provides information to the user that may be beneficial in the use of the instrument. DANGER ! Before operating the DigiLock 110 plug in module please read this manual carefully to CAUTION ! prevent from damage to the electronics, connected diode lasers and injury to persons. The following safety instructions must be followed at all times.

  • Page 11: Identification Of Manufacturer

    POS/NEG switch and the CURRENT/ POWER switch of the Current Control DCC 110. As long as the ON/OFF switches are set to position OFF, the laser diode is short-circuited by the relay integrated in the Toptica Diode Laser Head.

  • Page 12: Operator Controls And Connections

    Feedback Controlyzer DigiLock 110 Operator Controls and Connections Front Panel Figure 4 Front panel of the DigiLock 110 1 ON/OFF switch and indicator 6 Main 11 DIO high-speed analog output General purpose digital input/ output 2 Precise 7 Aux 12 Trigger output...

  • Page 13: Description Of Front Panel Operator Controls And Connectors

    CAUTION ! The ON/OFF switch (1) should only be used when the laser is switched off. Always first switch on the DigiLock 110 module, then start the DigiLock 110 software and after that switch on the laser and vice versa.

  • Page 14: Backplane Connections

    11.4 for details). This readout only works when the DigiLock 110 as well as the modules to be read out are installed on channel 1 of the rack (slot 2, 3 and 6). It is recommended to install the DigiLock 110 in slot 6 (see Figure 5).

  • Page 15: Digilock 110 Hardware Installation

    Before installation, switch off the laser and all other modules and disconnect the supply rack from the mains supply. The DigiLock 110 can be plugged into any slot of a 19’’ or 12’’ rack, except the one reserved for the DC 110/Mon on the right.

  • Page 16: Digilock 110 Software Installation

    USB-Driver Installation The DigiLock 110 provides a USB connection to load the firmware and to control the module via the sup- plied PC based software. In order to communicate with the DigiLock 110, the USB driver must be installed before the installation of the application software.

  • Page 17: Digilock 110 Control Architecture

    DUI has a built-in Remote Control Interface (RCI). Nearly all controls of the DMS and DUI can be accessed remotely by sending corresponding commands via a TCP/IP connection. A detailed descrip- tion of the RCI can be found in the DigiLock 110 RCI Manual which can be downloaded from the T OPTICA Photonics AG website.

  • Page 18: Digilock Module Server (Dms)

    "port number". For details of the remote control see the DigiLock 110 RCI Manual which can be downloaded from the T Photonics AG website. OPTICA In addition to the physically present DigiLocks it also lists a dummy to allow to start a DUI with no DigiLock 110 present. Page 14 Status: 5.12.17...

  • Page 19: Digilock User Interface (Dui)

    DigiLock User Interface (DUI) NOTE ! This DigiLock 110 manual refers to the software version 1.6.0 Visit www.toptica.com for information about the most recent software version. The DigiLock User Interface (DUI) consists of two main areas and a status bar. In the upper part of the screen the user can set the appropriate operation parameters of the selected function.

  • Page 20: General

    Feedback Controlyzer DigiLock 110 General 8.1.1 DigiLock User Interface Operation To operate the software efficiently it is necessary to be familiar with the DUI. Some helpful remarks are presented in the following: • Changing numeric input controls Set the focus on the desired numeric control (left click on the field). A cursor appears in the input field.

  • Page 21: Storage Of The Profile

    Start the new DigiLock 110 software When the new DigiLock 110 software is started for the first time, a default profile is loaded to the DigiLock 110 module. The former user specific profile of the old software version is saved as a backup (DigiLock-Profile_<ModuleSN>_SW<oldSWversion>_backup.pro) to the profiles directory (see section...

  • Page 22: Functions

    Feedback Controlyzer DigiLock 110 Functions In the upper part of the screen all the available functions and options of the DigiLock 110 are displayed on different layers. With the buttons on the left hand side you can select the desired function and then browse the corresponding options and parameters.
  • Page 23 The Spectrum is useful when the error signal is gener- ated by frequency modulation to select the peak/valley to lock to. If the error signal is generated in the DigiLock 110 the Spectrum can be Page 19...
  • Page 24 Feedback Controlyzer DigiLock 110 automatically selected to be the input of the frequency modulation module. Since the auto setting (see below) relies on the fact that the FM signal also carries the DC part, it is possible to manually select a different...
  • Page 25 Smart Assistance: Advanced Function Based on the settings (pos/neg, slope/extremum) the DigiLock 110 is automatically configured to lock to the nearest matching point. Engage: Uses an adapted trigger mechanism to engage the lock at the right moment to make the process insensitive to fluctuations.
  • Page 26 Feedback Controlyzer DigiLock 110 8.2.1.4 PID 1 Figure 12 PID 1 controller The PID 1 is a standard PID controller with the special feature that the user can set a cut-off frequency (I cut-off) below which the integral part is limited (as illustrated by the transfer function, section 8.2.2). This limitation of the integral part is important in case PID 1 is used together with PID 2 in one control system.
  • Page 27 8. DigiLock User Interface (DUI) Proportional gain. Integral gain. I cut-off: Frequency in Hz below which the integrator is limited. Activated by the checkbox. Derivative gain. NOTE ! If the gain parameters are out of range an error message is displayed in the controller tab. Note that the maximum response is a combination of all PID parameters.
  • Page 28 Feedback Controlyzer DigiLock 110 Rst (Reset): Reset PID checkbox: Enables the PID reset. Reset rate: Slope in Volt/second when resetting the outputs of PID 1 and PID 2 respectively. Finite rates restrict the reset speed of the PID outputs to avoid destabilization due to rapid changes, e.g.
  • Page 29 8. DigiLock User Interface (DUI) 8.2.1.5 PID 2 Figure 13 PID 2 controller The PID 2 controller is identical to PID 1. PID 2 does not have an integral cut-off frequency, because when combining two PID controllers this is only needed at the controller which has to drive the output with the higher bandwidth (usually PID 1).
  • Page 30 Figure 14 Analog controller In order to overcome the signal delay introduced by digital signal processing, the DigiLock 110 features a very fast analog path. Its high bandwidth allows the experienced user to achieve further improvements particularly in demanding locking situations. Note that an improvement of the lock relies on a corre- spondingly high error signal and actuator bandwidth.
  • Page 31 8. DigiLock User Interface (DUI) 8.2.1.7 Lock-In Figure 15 Left: Lock-in module Right: Schematic error signal of a single resonance generated with the Lock-In modulation technique The Lock-In module can be used to generate an error signal for the PID controller with the Lock-in modu- lation/demodulation scheme.
  • Page 32 Feedback Controlyzer DigiLock 110 8.2.1.8 PDH Figure 16 Left: PDH module Right: Schematic error signal of a single resonance generated with the Pound-Drever-Hall modulation technique. The sidebands - exaggerated for Illustration - can be seen at about 10 MHz. The principle of operation is similar to the Lock-In module but the modulation frequencies are typically higher than the characteristic linewidth of the resonance.

  • Page 33: Simulation (Controller Frequency Response)

    8. DigiLock User Interface (DUI) 8.2.2 Simulation (Controller Frequency Response) Figure 17 Simulation of the frequency response for optimization of the controller design. This function visualizes the transfer function of the selected PID controller according to the parameters chosen. The transfer function graph consists of two traces: the magnitude and the phase which are plot- ted versus the frequency.

  • Page 34: Response (Network Analysis)

    Feedback Controlyzer DigiLock 110 8.2.3 Response (Network Analysis) Figure 18 Response of the system to an additional sinosoidal pertubation (network analysis) In order to determine the dynamic behavior of a system, it is a common strategy to perform a network analysis, i.e.

  • Page 35: System

    Schematic of the high-speed signal path inside the DigiLock 110 module indicating the current configu- ration. Some parameters can only be set on this screen (<Main in> input offset, <Main in> gain, invert sig- nal, all kinds of filters).

  • Page 36: Settings

    Feedback Controlyzer DigiLock 110 8.2.5 Settings The Settings function enables the user to access additional options of the DigiLock 110. It is splitted into the following six tabs according to the affected functionality: 8.2.5.1 PID 1. On this tab all advanced parameters for the PID modules can be set.
  • Page 37 8. DigiLock User Interface (DUI) 8.2.5.2 LI/PDH Figure 21 LI/PDH tab in the Settings function Modulation signal type: Type of the waveform used for modulation and demodulation. First filter notch (LI-Module): The LI module only works properly if a low-pass filter is applied to the demodulated signal in order to filter frequency components located at the modulation frequency.
  • Page 38 Feedback Controlyzer DigiLock 110 8.2.5.4 Display On this tab the settings for displaying the data can be chosen. Figure 23 Display tab in the Settings function Update rate: Rate at which new data sets are displayed in the various graphs.
  • Page 39 DUI is hidden in order to avoid unnecessary traffic on the USB. However for some reasons it is desired to acquire data nevertheless, e.g. operat- ing the DUI remotely (see DigiLock 110 RCI Manual which can be down- loaded from the T Photonics AG website).
  • Page 40 Feedback Controlyzer DigiLock 110 8.2.5.6 Visibility Modules included in the software that are not used in a specific application might distract the user. Therefore the visibility status of some modules can be configured. Figure 25 Visibility tab in the Settings function Module and Function visibility: Show or hide the respective functions and modules.
  • Page 41 8. DigiLock User Interface (DUI) Figure 27 Dialog window to select the profile source file and the parameters to be imported Page 37 Status: 5.12.17...

  • Page 42: Display Area

    Feedback Controlyzer DigiLock 110 Display Area The lower part of the screen shows three different displays that are accessible through the buttons on the left hand side. 8.3.1 Scope Figure 28 Scope display Two channel digital oscilloscope to display different available system signals.

  • Page 43: Autolock

    8. DigiLock User Interface (DUI) 8.3.2 AutoLock Figure 29 AutoLock display This display is used in conjunction with the AutoLock module in the upper part of the screen. In this display the user can handle two major tasks: • Search the desired lock point via panning and zooming the displayed signal. •...

  • Page 44: Spectrum

    Feedback Controlyzer DigiLock 110 8.3.3 Spectrum Figure 30 Spectrum display The Spectrum displays the fast fourier transform (FFT) of the signal. The functionality is similar to the Scope display but in the frequency domain. NOTE ! The selected frequency range defines the sampling rate of the signal used for the FFT.

  • Page 45: Notes On Feedback Control Loops With The Digilock 110

    50 Ohms wave guide and to avoid extra cable length in the signal path. The fast inputs and out- puts of the DigiLock 110 are 50 Ohms in the standard setting upon delivery. If necessary, they can be changed to high impedance by appropriate settings of internal jumpers (for details please see section 11.2).

  • Page 46: Controller Parameter Adjustment And Optimization

    The output of the controller is a weighted sum of the integral (I), proportional (P) and differential (D) paths scaled by the overall gain. The digital PIDs in the DigiLock 110 allow for a precise and reproducible control of the gain settings.

  • Page 47: Identification Of Signal Polarity And Slope

    Otherwise the direction has to be determined for the particular actuator used. For example, if the DigiLock 110 Scan module scans the laser via the Scan Control SC 110 and the output of PID 2 is also chosen to be the SC 110, its polarity is trivially positive. If the output of PID 1 is then directed to the current of the laser diode, the polarity of the controller will depend on the polarity of the laser diode as defined by the DCC 110 current control (see Sys DC 110 manual for details).
  • Page 48 The opposite is true for locking onto the posi- tive slopes (dotted green). The traces have successively been exported from the Scope dis- play of the DigiLock 110 (right click on scope graph). Page 44...
  • Page 49 NOTE ! The AutoLock mode of the DigiLock 110 expects a consistent choice of the polarity setting for all PID controllers involved, see above. Once the overall polarity is found, a correction of the polarity can be compensated by changing the slope also.

  • Page 50: Relock Feature

    Feedback Controlyzer DigiLock 110 Relock Feature The basis of the relock feature of the DigiLock 110 is the out of lock detection. It is based on a window comparator which is defined by four parameters (see Figure 34): • Level out Max •...

  • Page 51: Signal Limitations In Analyzing The Locking Performance

    This effect is well known from digital oscilloscopes. In the case of the DigiLock 110 there is an additional effect to be observed for sampling rates well below the Nyquist frequency (especially using PDH modulation): Due to the complete synchrony of the sampling with the applied modulation the undersampled signal can show as a (noisy) line at a finite off- set that varies from shot to shot.

  • Page 52: Application Examples

    Typical setup for laser locking The signal from the photo detector (PD) is fed into the <Main in> input of the DigiLock 110. The two PID controllers act via the backplane and SC 110 on the grating piezo and via the <Main out>...
  • Page 53 For the standard path to the default profile (DigiLock-Profile_default.pro) see section 11.5. 10. The current and temperature settings of the laser can be remotely controlled via the DigiLock 110 module. To do so, the associated backplane channels have to be activated by setting the corresponding internal jumpers (see section 11.2).
  • Page 54 SC 110 as a high voltage amplifier. The output is the sum of the voltage specified in the DigiLock 110 software and the offset of the SC 110. The SC 110 offset can hence additionally be used to scan the laser.
  • Page 55 10. Application Examples Figure 36 DigiLock user interface (DUI) after startup. Here, the laser is scanned across the saturated absorption lines of Rb at 780.24 nm, see sec- tion 10.2. Figure 37 Graphical overview of the signal path through the controller (System function) The System function (Figure 37) shows a block diagram of the control loop.
  • Page 56 Feedback Controlyzer DigiLock 110 Name Description Standard Value Input offset Offset to be subtracted from the input signal 0.0 V before digitalization to reduce the signal offset for further analog amplification Gain Analog gain to amplify the signal to take advan-...

  • Page 57: Doppler-Free Saturation Spectroscopy

    The Scope display provides a two channel oscilloscope and is a general tool to view a variety of signals of the DigiLock 110. To display the spectroscopy signal use a timescale of 50 ms (corre- sponding to the 10 Hz scan frequency), choose <Main in> as CH 1 and <SC 110 out> as CH 2. The scope triggers on the rising slope of the internal scan ramp.

  • Page 58: 10.2.1 Side Of Fringe Locking

    Once the laser scans across the spectral function two different locking schemes can be implemented using the AutoLock module of the DigiLock 110. First locking to the side of a fringe is presented (section 10.2.1) then the use of frequency modulation/demodulation to lock to a maximum or minimum is explained (section 10.2.2).
  • Page 59 10. Application Examples First the AutoLock module is activated and the controllers PID 1 and PID 2 are selected by check- ing the corresponding boxes (see Figure 40). PID 1 will handle the high frequencies (by controlling the laser current via the modulation option in the laser head) whereas PID 2 will be responsible for the lower frequencies by controlling the piezo voltage.
  • Page 60 Feedback Controlyzer DigiLock 110 To configure the PID controllers, select the PID 1/PID 2 tab (see Figure 11 and Figure 13) to access the corresponding parameters (see Figure 43). A valid strategy is to first implement PID 2 for initial locking (setting the Gain of PID 1 to zero) and then add PID 1 to improve the lock at higher fre- quencies.
  • Page 61 10. Application Examples Figure 44 Initiating the AutoLock to a slope of the absorption signal Figure 45 Autolock display just after the lock is engaged (PID: lock to slope) After some time the yellow trace disappears and a scatter plot is left which indicates both the input signal (y-axis) and the current output of the PID 2 which in this case coincides with the scan (see Figure 46) on the x-axis.
  • Page 62 Feedback Controlyzer DigiLock 110 Figure 46 AutoLock display while the lock is active. The yellow scatter plot indicates signal input and regulator output (PID 2) Parameter optimization: To obtain a “good“ lock it is necessary to increase the gain settings of the PID controllers to the highest possible values without oscillations (see section 9 for details).

  • Page 63: Top Of Fringe Locking (Lock-In)

    10 of the characteristic linewidth. In this example a frequency of about 100 kHz is used. Due to the specific architecture of the DigiLock 110 only discrete frequencies are possible. Type in the desired one and the system will automatically determine the nearest one available (Act freq).
  • Page 64 NOTE ! As of software versions 1.5.4.70 the DigiLock 110 frequency modulation modules feature an automatic phase adjust (see section 8.2.1.7 and 8.2.1.8 for details). Please see section 9.2 on how to manually adjust the phase.
  • Page 65 10. Application Examples To initiate the lock, perform a right mouse click to access the context menu and select LI/PDH: Lock to extremum. The trace changes its color (here from yellow to blue) to show that the actual trace is captured in the background. During the next scan the lock is triggered. Figure 51 shows the AutoLock display while the lock is triggered.

  • Page 66: Pound-Drewer-Hall Stabilization To A Cavity

    Experimental setup of a Pound-Drewer-Hall (PDH) stabilization to a cavity. Note that the modulation is directly added to the <Main out> channel of the DigiLock 110. Alternatively the modulation can be applied to the mod AC input of the DLpro.
  • Page 67 10. Application Examples The parameters of the PDH module are analogous to the LI module and are listed in the following table. Name Description Value to set to Input Signal input to be demodulated <Main In> Set freq Modulation set frequency can be selected for a set of 12.5 [MHz] 5 discrete modulation frequencies Amplitude...
  • Page 68 Feedback Controlyzer DigiLock 110 Figure 54 AutoLock display of the reflection signal of a Fabry-Perot cavity (upper yellow trace) with the corresponding PDH-signal (lower red trace) 18a. The phase between the modulation and the reference signal must be adjusted to obtain a large, symmetric error signal with steep slopes at the maximum of the spectral signal.
  • Page 69 10. Application Examples Figure 55 Initiating the automatic PDH-Lock to extremum Figure 56 AutoLock display after triggering the lock (LI/PDH: Lock to extremum) Page 65 Status: 5.12.17...

  • Page 70: Appendix

    11.2 Internal Jumpers The DigiLock 110 module is shipped with a standard configuration of its inputs and outputs. The internal jumpers allow to modify this configuration. The table below shows all jumpers and their function. For loca- tion of the jumpers and their positions please see Figure 57 and Figure 58.

  • Page 71: Digilock 110 Pcbs

    11. Appendix 11.3 DigiLock 110 PCBs 11.3.1 Baseboard Figure 57 Jumpers and their positions on DigiLock 110 Baseboard Page 67 Status: 5.12.17...

  • Page 72: 11.3.2 Plug-On Board

    Feedback Controlyzer DigiLock 110 11.3.2 Plug-On Board Figure 58 Jumpers and their positions on DigiLock 110 Plug-On Board Page 68 Status: 5.12.17...

  • Page 73: Specifications Of Digilock 110 Connections

    11. Appendix 11.4 Specifications of DigiLock 110 Connections Power Supply Value Supply Voltage +-15 V Supply Current 700 mA +15V (max) Supply Current 200 mA -15V (max) Input Resolution Sample Bandwidth Range Input Comment Channel [bit] Rate [Hz] (Typ.) (Typ.)

  • Page 74: Directories Of The Digilock 110 Software

    Feedback Controlyzer DigiLock 110 11.5 Directories of the DigiLock 110 Software NOTE ! %SystemDrive% refers to the harddrive partition where Windows and the user specific application data are installed, typically C:\. <UserProfile> is the currently active Windows user account. English Version...

  • Page 75: Pin Assignment Of The Digilock 110 Backplane

    11. Appendix 11.6 Pin Assignment of the DigiLock 110 Backplane Actual pins needed for normal operation of the DigiLock 110 Module are marked with a grey back- ground color. (VG-64-a/b/c standard connector according to IEC 60603-2) Figure 59 VG-64-a/b/c standard connector...

  • Page 76: Declaration Of Ce Conformity

    Feedback Controlyzer DigiLock 110 11.7 Declaration of CE Conformity Page 72 Status: 5.12.17...

  • Page 77: Eu Legislation For Electrical And Electronic Equipment (Eee)

    11. Appendix 11.8 EU Legislation for Electrical and Electronic Equipment (EEE) Companies selling electrical and electronic goods in the European Union must conform to the EU legisla- tion for electrical and electronic equipment (EEE), which includes the Waste Electrical and Electronic Equipment Directive (WEEE).

  • Page 78: Guarantee And Service

    Return Material Authorization (RMA) number for you. You can contact us in the following ways: - Internet: service.toptica.com. In our support section you can find a list of frequently asked ques- tions and a service contact form - Email: service@toptica.com...

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