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d2:laser_controller [2020/05/29 21:47] – Michael Radunskyd2:laser_controller [2020/10/29 21:09] – Michael Radunsky
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 [[http://www.vescent.com/products/electronics/d2-105-laser-controller/|D2-105 web page]] [[http://www.vescent.com/products/electronics/d2-105-laser-controller/|D2-105 web page]]
  
-===== Description: =====+==== Description: ====
  
 The laser controller has two temperature controllers capable of sub-mK stability(( Sub-mK stability requires a proper thermal design and proper tuning of the temperature controller to the thermal plant. If you did not purchase a D2-100 Diode Laser with your Laser Controller, please read the section on tuning the temperature controller.)) and a 200 mA or 500 mA precision current source based on the Libbrecht-Hall(( Libbrecht and Hall, A Low-Noise, High-Speed Current Controller, Rev. Sci. Inst. 64, pp. 2133-2135 (1993).)) circuit.  The laser controller is designed for very fast current modulation via the servo input enabling high-speed servo control of the laser's frequency.  The current servo input can accommodate input frequencies over 10 MHz and is limited by  the 1 kΩ input impedance. Additionally, an RF port is available for higher frequency modulation. The laser controller has two temperature controllers capable of sub-mK stability(( Sub-mK stability requires a proper thermal design and proper tuning of the temperature controller to the thermal plant. If you did not purchase a D2-100 Diode Laser with your Laser Controller, please read the section on tuning the temperature controller.)) and a 200 mA or 500 mA precision current source based on the Libbrecht-Hall(( Libbrecht and Hall, A Low-Noise, High-Speed Current Controller, Rev. Sci. Inst. 64, pp. 2133-2135 (1993).)) circuit.  The laser controller is designed for very fast current modulation via the servo input enabling high-speed servo control of the laser's frequency.  The current servo input can accommodate input frequencies over 10 MHz and is limited by  the 1 kΩ input impedance. Additionally, an RF port is available for higher frequency modulation.
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-===== Purchase Includes: =====+==== Purchase Includes: ====
 <WRAP group> <WRAP group>
 <WRAP half column> <WRAP half column>
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 </WRAP></WRAP> </WRAP></WRAP>
  
-===== Absolute Maximum Ratings =====+==== Absolute Maximum Ratings ====
 Note: All modules designed to be operated in laboratory environment Note: All modules designed to be operated in laboratory environment
 <WRAP center round box 60%> <WRAP center round box 60%>
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 </WRAP> </WRAP>
  
-=====Specifications=====+====Specifications====
 <WRAP center round box 550px> <WRAP center round box 550px>
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 </WRAP> </WRAP>
  
-===== Inputs, Outputs, and Controls =====+==== Inputs, Outputs, and Controls ====
  
 [{{ :d2:d2-105:d2-105-frontback-diagram.png?nolink&900 |Front and Back Panel of D2-105}}] [{{ :d2:d2-105:d2-105-frontback-diagram.png?nolink&900 |Front and Back Panel of D2-105}}]
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 **Laser Temp Output (8-pin connector)** **Laser Temp Output (8-pin connector)**
  
-An 8-pin Hirose connector (see <tabref TECconnectortable> for identity of connectors) carries the signals for the temperature control of the Laser module.  The wiring diagrams are shown in the table below, where 1 (2) refer to stage 1 (2) temperature control, which stabilizes the Laser Housing (Laser Diode). Rth and Rth_Rtn are the two ends of a 10 kΩ [[http://www.analogtechnologies.com/ath10kr8.html|Analog Technologies ATH10KR8 Thermistor]].+An 8-pin Hirose connector (see <tabref TECconnectortable> for identity of connectors) carries the signals for the temperature control of the Laser module.  The wiring diagrams are shown in <tabref TEC_connector_pinout> below, where 1 (2) refer to stage 1 (2) temperature control, which stabilizes the Laser Housing (Laser Diode). Rth and Rth_Rtn are the two ends of a 10 kΩ [[http://www.analogtechnologies.com/ath10kr8.html|Analog Technologies ATH10KR8 Thermistor]].
  
 <WRAP round center box 230px><tabcaption TEC_connector_pinout| TEC connector pin out> <WRAP round center box 230px><tabcaption TEC_connector_pinout| TEC connector pin out>
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 The Servo Input on the front panel continues to function when the SETPOINT ENABLE is pulled low.  Only the Coarse and Fine Current Adjustments are disabled. The Servo Input on the front panel continues to function when the SETPOINT ENABLE is pulled low.  Only the Coarse and Fine Current Adjustments are disabled.
  
-=====Turning on the Laser Diode=====+====Turning on the Laser Diode====
  
 In compliance with FDA requirements for a Class 3B laser, the Laser Controller has two safety interlocks. If either interlock is tripped, the laser will turn off and stay off until the interlocks are reset AND the laser switch is switched from the "off / reset" position to the "on" position. Additionally, if the Laser Controller loses power, the laser diode will remain off when power is restored. In compliance with FDA requirements for a Class 3B laser, the Laser Controller has two safety interlocks. If either interlock is tripped, the laser will turn off and stay off until the interlocks are reset AND the laser switch is switched from the "off / reset" position to the "on" position. Additionally, if the Laser Controller loses power, the laser diode will remain off when power is restored.
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 To get good temperature stability, the temperature servo response needs to be tuned to match the thermal load. Access to tuning the temperature response is provided on the right side panel of the Laser Controller and requires removing that side panel to access the controls. The Laser Controller provides two independent temperature controllers that are nominally identical. However, stage 2 has front panel adjustment of the temperature set-point, while the stage 1 temperature set-point is a side-panel adjustment. Additionally, the front panel TEMP SERVO INPUT adjusts the stage 2 set-point while stage 1 does not have an equivalent function. Stage 2 is accessed in the middle of the side-panel, while stage 1 is near the back of the side panel. Typically, stage 2 is used to control the laser temperature and stage 1 is used to control the temperature surrounding stage 2.  In this way temperature gradients between the laser diode and the thermistor measuring the laser temperature are stabilized and temperature changes caused by room temperature drift are greatly reduced.  To get good temperature stability, the temperature servo response needs to be tuned to match the thermal load. Access to tuning the temperature response is provided on the right side panel of the Laser Controller and requires removing that side panel to access the controls. The Laser Controller provides two independent temperature controllers that are nominally identical. However, stage 2 has front panel adjustment of the temperature set-point, while the stage 1 temperature set-point is a side-panel adjustment. Additionally, the front panel TEMP SERVO INPUT adjusts the stage 2 set-point while stage 1 does not have an equivalent function. Stage 2 is accessed in the middle of the side-panel, while stage 1 is near the back of the side panel. Typically, stage 2 is used to control the laser temperature and stage 1 is used to control the temperature surrounding stage 2.  In this way temperature gradients between the laser diode and the thermistor measuring the laser temperature are stabilized and temperature changes caused by room temperature drift are greatly reduced. 
  
-====Transfer Function and Poles====+===Transfer Function and Poles===
  
 Each stage of temperature control has a transfer function shown below: Each stage of temperature control has a transfer function shown below:
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 <imgcaption side_adjustb|Side Panel Adjustment of Poles for D2-105>{{:d2:d2-105:temppoles4.jpg?nolink&300}}</imgcaption> <imgcaption side_adjustb|Side Panel Adjustment of Poles for D2-105>{{:d2:d2-105:temppoles4.jpg?nolink&300}}</imgcaption>
 </WRAP> </WRAP>
-====User Control of the Poles and Gain====+===User Control of the Poles and Gain===
  
 If you remove the right side panel on the Laser Controller, for each stage of temperature control, you will see the panel shown in <imgref side_adjustb>. The set of click switches labeled "Integral" controls the PI (ω<sub>1</sub>) pole. <color black/yellow>Clicking the first switch, labeled "proportional," into the on position removes the integral gain (but not the differential gain). If the "proportional" switch is in the off position (integral gain is now on), then the sum of the times for all switches in the on position gives the RC time-constant for the PI pole.</color> For example, if the 2<sup>nd</sup> (0.47s) switch and the 4<sup>th</sup> (2.2s) switch are in the on position (and the rest off), then the time constant is 2.7s and ω<sub>1</sub> = 1/2.7s = 0.37 Hz.  If you remove the right side panel on the Laser Controller, for each stage of temperature control, you will see the panel shown in <imgref side_adjustb>. The set of click switches labeled "Integral" controls the PI (ω<sub>1</sub>) pole. <color black/yellow>Clicking the first switch, labeled "proportional," into the on position removes the integral gain (but not the differential gain). If the "proportional" switch is in the off position (integral gain is now on), then the sum of the times for all switches in the on position gives the RC time-constant for the PI pole.</color> For example, if the 2<sup>nd</sup> (0.47s) switch and the 4<sup>th</sup> (2.2s) switch are in the on position (and the rest off), then the time constant is 2.7s and ω<sub>1</sub> = 1/2.7s = 0.37 Hz. 
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-====Tuning the Thermal Loop====+===Tuning the Thermal Loop===
  
 Although there are numerous methods for tuning the loop parameters, these instructions will use the Ziegler-Nichols tuning method. Although there are numerous methods for tuning the loop parameters, these instructions will use the Ziegler-Nichols tuning method.
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 //NOTE: Depending on the thermal design, nested temperature loops can fight each other, causing oscillations and instability. If you observe this, you will need to reduce the gain and/or increase the time-constants on the slower stage. // //NOTE: Depending on the thermal design, nested temperature loops can fight each other, causing oscillations and instability. If you observe this, you will need to reduce the gain and/or increase the time-constants on the slower stage. //
  
-====Tuning Temperature Loop for Photodigm Mercury Lasers====+===Tuning Temperature Loop for Photodigm Mercury Lasers===
  
 If you are using the D2-105 laser controller to drive a Photodigm Mercury laser in a TOSA package, the following may be helpful as a starting point for setting the thermal control loop parameters.((Courtesy of [[http://www.photodigm.com|Photodigm]]))  Refer to <imgref side_adjustb>. If you are using the D2-105 laser controller to drive a Photodigm Mercury laser in a TOSA package, the following may be helpful as a starting point for setting the thermal control loop parameters.((Courtesy of [[http://www.photodigm.com|Photodigm]]))  Refer to <imgref side_adjustb>.
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 If the Temperature with the above TIME settings begins to run away, then quickly turn the “PROPGAIN” Potentiometer CCW until it stabilizes. If the Temperature with the above TIME settings begins to run away, then quickly turn the “PROPGAIN” Potentiometer CCW until it stabilizes.
 +
 +We use [[https://www.photodigm.com|Photodigm DBR lasers]]. \\
 +[[https://www.photodigm.com|{{:d2:d2-100:photodigm_logo.png?direct&200|}}]]
 +
d2/laser_controller.txt · Last modified: 2024/03/27 15:33 by Thomas Bersano