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d2:laser_servo [2019/02/21 15:55] – [Right Side Panel] Michael Radunskyd2:laser_servo [2021/12/17 01:58] (current) – external edit 127.0.0.1
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 The D2-125 Reconfigurable Laser Servo contains a tunable PI<sup>2</sup>D loop filter for tight locking to an error signal. The error signal is either an amplified version of the Error Input signal (side-lock mode) or an amplified version of a demodulated Error Input (optional peak-lock mode). In both modes, a DC Offset is summed to the error signal, allowing the user to select the zero-crossing and thus the lock point. The error signal can also be inverted via a front-panel switch. Additionally, the Laser Servo has an internal ramp generator for sweeping the output and computer control functionality to make and break lock and directly control the output voltage.  The D2-125 Reconfigurable Laser Servo contains a tunable PI<sup>2</sup>D loop filter for tight locking to an error signal. The error signal is either an amplified version of the Error Input signal (side-lock mode) or an amplified version of a demodulated Error Input (optional peak-lock mode). In both modes, a DC Offset is summed to the error signal, allowing the user to select the zero-crossing and thus the lock point. The error signal can also be inverted via a front-panel switch. Additionally, the Laser Servo has an internal ramp generator for sweeping the output and computer control functionality to make and break lock and directly control the output voltage. 
  
-The main component in the Reconfigurable Laser Servo is the PI<sup>2</sup>D loop filter, which means that the feedback has standard proportional (P), integral (I), and differential (D) feedback with a second integral feedback (I) providing the  PI<sup>2</sup>D transfer function. The double integration is used to boost gain at low frequencies.  With integrator frequencies tunable from 2 MHz down to 10 Hz, the Laser Servo can be optimized to a wide variety of plants and servo loops. With the Peak Lock option, the Laser Servo can demodulate a provided 4 MHz dither signal to enable slope-detection for locking to signal minimas and maximas. The Laser Servo can be used to lock a laser's current or PZT to an interferometer or an optical transition. With peak-lock, the Laser Servo can perform Pound-Drever-Hall (PDH) locking to an optical cavity. The Reconfigurable Laser Servo uses basic voltage inputs and outputs.  As a result, it can be used with lasers or with any voltage-tunable device with an error signal.+The main component in the Reconfigurable Laser Servo is the PI<sup>2</sup>D loop filter, which means that the feedback has standard proportional (P), integral (I), and differential (D) feedback with a second integral feedback (I) providing the  PI<sup>2</sup>D transfer function. The double integration is used to boost gain at low frequencies.  With integrator frequencies tunable from 2 MHz down to 10 Hz, the Laser Servo can be optimized to a wide variety of plants and servo loops. With the Peak Lock option, the Laser Servo can demodulate a provided 4 MHz dither signal to enable slope-detection for locking to signal minima and maxima. The Laser Servo can be used to lock a laser's current or PZT to an interferometer or an optical transition. With peak-lock, the Laser Servo can perform Pound-Drever-Hall (PDH) locking to an optical cavity. The Reconfigurable Laser Servo uses basic voltage inputs and outputs.  As a result, it can be used with lasers or with any voltage-tunable device with an error signal.
  
 The Laser Servo can be unlocked by a computer (via TTL control) to jump the output voltage to a set voltage difference from the current lock point, or to a specific voltage. This feature can be used to jump the laser frequency a known distance away and then relock to the original or a new lock point frequency. This feature can be used for auto-locking or relocking routines.  The Laser Servo can be unlocked by a computer (via TTL control) to jump the output voltage to a set voltage difference from the current lock point, or to a specific voltage. This feature can be used to jump the laser frequency a known distance away and then relock to the original or a new lock point frequency. This feature can be used for auto-locking or relocking routines. 
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 <WRAP center round box 600px> <WRAP center round box 600px>
 |                                                                                                  |  **Value**                                                                                                                          **Units**  | |                                                                                                  |  **Value**                                                                                                                          **Units**  |
-| **Input and Output Impedance**                                                                    50((~500 Ω input impedance for negative gain))                                                                                    |  Ω          |+| **Input and Output Impedance**                                                                    50((In Peak Lock mode, the 50 Ω to ground is AC-coupled.  A measurement of the DC impedance will yield a higher value.))                                                                                    |  Ω          |
 | **Output Voltage (main and aux)**                                                                |  ±10                                                                                                                                V          | | **Output Voltage (main and aux)**                                                                |  ±10                                                                                                                                V          |
 | **Input Voltage Noise**(( Referenced to 50Ω load))                                                <5                                                                                                                                |  nV/√Hz     | | **Input Voltage Noise**(( Referenced to 50Ω load))                                                <5                                                                                                                                |  nV/√Hz     |
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 Located at the top of the front panel, the monitor section contains 6 BNC outputs for monitoring various signals used by the Laser Servo. The logic of the monitors is shown in <imgref image1> Open a {{d2:d2-125:d2-125_monitor_logic.pdf|pdf of this image }}. Located at the top of the front panel, the monitor section contains 6 BNC outputs for monitoring various signals used by the Laser Servo. The logic of the monitors is shown in <imgref image1> Open a {{d2:d2-125:d2-125_monitor_logic.pdf|pdf of this image }}.
  
-<WRAP center round box 420px><imgcaption image1|Monitor output logic>{{ d2:d2-125:d2-125_monitor_logic.jpeg?400|}}</imgcaption></WRAP>+<WRAP center round box 420px><imgcaption image1|Monitor output logic>{{ d2:d2-125:d2-125_monitor_logic.jpeg?600|}}</imgcaption></WRAP>
  
 **Error In** **Error In**
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 **Auxiliary Servo Output** **Auxiliary Servo Output**
  
-The AUXILIARY SERVO OUTPUT is generated from integrating the SERVO OUTPUT.  Its purpose is to supply a correction signal to drive the SERVO OUTPUT to zero. When used with Vescent DBR lasers and the D2-105 Laser Controller, the AUXILIARY SERVO OUTPUT can be connected to the TEMP SERVO IN to adjust the laser diode temperature to keep the feedback laser current constant. Similarly, AUXILIARY SERVO OUTPUT can drive a PZT on an external-cavity laser diode to keep the laser diode current constant. See [[d2:laser_servo#Aux Gain: + / Aux Gain - (2-position switch)|AUXILIARY SERVO: GAIN SIGN]] and [[d2:laser_servo#Auxiliary Servo: Gain (25-turn trimpot)|AUXILIARY SERVO: GAIN]] for information on setting the gain and and gain sign of the AUXILIARY SERVO OUTPUT.+The AUXILIARY SERVO OUTPUT is generated from integrating the SERVO OUTPUT.  Its purpose is to supply a correction signal to drive the SERVO OUTPUT to zero. When used with Vescent DBR lasers and the D2-105 Laser Controller, the AUXILIARY SERVO OUTPUT can be connected to the TEMP SERVO IN to adjust the laser diode temperature to keep the feedback laser current constant. Similarly, AUXILIARY SERVO OUTPUT can drive a PZT on an external-cavity laser diode to keep the laser diode current constant. See [[d2:laser_servo#Aux Gain: + / Aux Gain - (2-position switch)|AUXILIARY SERVO: GAIN SIGN]] and [[d2:laser_servo#Auxiliary Servo: Gain (25-turn trimpot)|AUXILIARY SERVO: GAIN]] for information on setting the gain and gain sign of the AUXILIARY SERVO OUTPUT.
  
 **Ramp Offset**  **Ramp Offset** 
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 ===Auxiliary Servo: Gain (25-turn trimpot)=== ===Auxiliary Servo: Gain (25-turn trimpot)===
  
-This trimpot sets the gain for the AUXILIARY SERVO OUTPUT. The Aux Servo is a pure integrator and the gain ranges from 500 μs to 5 s.+This trimpot sets the gain for the AUXILIARY SERVO OUTPUT. The Aux Servo is a pure integrator and the gain ranges from 500 μs to 5 s.  Full ccw sets gain to minimum (5 s), full cw sets gain to maximum (500 µs).
  
 <WRAP center round box 420px><imgcaption d2_125_side_panel_photo|Certain rarely used controls are only accessible by removing the right-side panel, as shown in the figure above.> <WRAP center round box 420px><imgcaption d2_125_side_panel_photo|Certain rarely used controls are only accessible by removing the right-side panel, as shown in the figure above.>
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 ** Aux: Bipolar / Aux: Unipolar (2-position slider switch) ** ** Aux: Bipolar / Aux: Unipolar (2-position slider switch) **
  
-This 2-position slider switch is only accessible by removing the right side panel (see above) and sets whether the AUXILIARY OUTPUT SERVO is unipolar or bipolar. It is factory set to be bipolar so the auxiliary output can range from -12 V to +12 V.  For some applications such as driving a PZT, limiting the voltage range to positive values is necessary.  When this switch is in the unipolar mode, the auxiliary output ranges from -0.5 V to +12 V. Additionally, when in Ramp->Aux mode and Aux: Unipolar, the ramp is centered at ~3.5V instead of 0V.+This 2-position slider switch is only accessible by removing the right side panel (see above) and sets whether the AUXILIARY OUTPUT SERVO is unipolar or bipolar. It is factory set to be bipolar so the auxiliary output can range from -10 V to +10 V.  For some applications such as driving a PZT, limiting the voltage range to positive values is necessary.  When this switch is in the unipolar mode, the auxiliary output ranges from -0.5 V to +10 V. Additionally, when in Ramp->Aux mode and Aux: Unipolar, the ramp is centered at ~3.5V instead of 0V.
  
 **Ramp Master / Slave (Jumper)** **Ramp Master / Slave (Jumper)**
  
-This jumper is only accessible by removing the right side panel (see above) and sets whether the ramp input is in master or slave mode. It is factory set to be in MASTER MODE. In SLAVE MODE (jumper off) the RAMP signal is generated externally and input through the back panel RAMP I/O port. In MASTER MODE (jumper on) the ramp is generated internally and is sent out to the RAMP I/O port for driving other D2-125 Laser Servos configured in SLAVE MODE.+This jumper is only accessible by removing the right side panel (see above) and sets whether the ramp input is in master or slave mode. It is factory set to be in MASTER MODE. In SLAVE MODE (jumper off) the RAMP signal is generated externally and input through the back panel RAMP I/O port. In MASTER MODE (jumper on) the ramp is generated internally and is sent out to the RAMP I/O port for driving other D2-125 Laser Servos configured in SLAVE MODE.   
 + 
 +The amplitude of the slave ramp is about -5x of the master ramp input (at slave Ramp Amp maximum).  The DC offset is applied after amplification.
  
 ====Lock Guard==== ====Lock Guard====
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 <WRAP center round box 400px> <WRAP center round box 400px>
 |  **C**  |  **B**  |  **A**  |  ** Hold Time**  |  **N+1 Relock Time**  | |  **C**  |  **B**  |  **A**  |  ** Hold Time**  |  **N+1 Relock Time**  |
-|0ff|0ff|0ff|  60 µs  |  150 µs  | +|Off|Off|Off|  60 µs  |  150 µs  | 
-|0ff|0ff|0n|  125µs  |  300 µs  | +|Off|Off|On|  125µs  |  300 µs  | 
-|0ff|On|0ff|  250 µs  |  600 µs  | +|Off|On|Off|  250 µs  |  600 µs  | 
-|0ff|0n|0n|  500 µs  |  1.25 ms  | +|Off|On|On|  500 µs  |  1.25 ms  | 
-|0n|0ff|0ff|  1 ms  |  2.5 ms  | +|On|Off|Off|  1 ms  |  2.5 ms  | 
-|0n|0ff|0n|  2 ms  |  5 ms  | +|On|Off|On|  2 ms  |  5 ms  | 
-|0n|On|0ff|  4 ms  |  10 ms  | +|On|On|Off|  4 ms  |  10 ms  | 
-|0n|0n|0n|  8 ms  |  20 ms  |+|On|On|On|  8 ms  |  20 ms  |
 </WRAP> </WRAP>
  
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 {{ :d2:d-sub_power_pinout.jpg?nolink&150 |}} {{ :d2:d-sub_power_pinout.jpg?nolink&150 |}}
 +
 +
 +While it is infrequent, the D2-005 power supply may occasionally radiate noise from the side of its chassis onto nearby electronics. This only occurs in some system configurations, and will appear as a signal at the frequency of your mains electricity (typically either 50 Hz or 60 Hz). This noise can easily be removed by moving the D2-005 at least 18 inches (45cm) away from other electronics, rotating it 90° such that the sides of the D2-005 face away, or by moving the entire power supply to a different shelf. To accommodate this, all D2-005's are shipped with a 5' DB9 cable as of January 1, 2022. 
  
 **Absolute Jump TTL (BNC)** **Absolute Jump TTL (BNC)**
  
-When asserted HIGH (5V) while in LOCK mode, ABSOLUTE JUMP takes the Laser Servo out of lock and conveys the voltage on LASER JUMP AMPLITUDE to the SERVO OUTPUT.  Thus, a 1 V input to LASER JUMP AMPLITUDE applies 1 V  to SERVO OUTPUT.  ABSOLUTE JUMP is useful when one wants to control the voltage on the integration stages of the loop filter, or for zeroing the integrators during auto-locking routines. When returned to LOW (0V), the loop filter is reengaged. Engaging or disengaging the ABSOLULTE JUMP is achieved in under 400 μs.+When asserted HIGH (5V) while in LOCK mode, ABSOLUTE JUMP takes the Laser Servo out of lock and conveys <color black/yellow>the negative</color> of the voltage on LASER JUMP AMPLITUDE to the SERVO OUTPUT.  Thus, a 1 V input to LASER JUMP AMPLITUDE applies -1 V  to SERVO OUTPUT.  ABSOLUTE JUMP is useful when one wants to control the voltage on the integration stages of the loop filter, or for zeroing the integrators during auto-locking routines. When returned to LOW (0V), the loop filter is reengaged. Engaging or disengaging the ABSOLUTE JUMP is achieved in under 400 μs.
  
-When asserted HIGH (5V) while in RAMP mode, ABSOLULTE JUMP applies a DC offset equal to the LASER JUMP AMPLITUDE to the ramp signal at SERVO OUTPUT. When asserted LOW while in RAMP mode, the ramp signal is DC balanced.+When asserted HIGH (5V) while in RAMP mode, ABSOLUTE JUMP applies a DC offset equal to -1*(LASER JUMP AMPLITUDEto the ramp signal at SERVO OUTPUT. When asserted LOW while in RAMP mode, the ramp signal is DC balanced.
  
-When disconnected, ABSOLULTE JUMP is low. +When disconnected, ABSOLUTE JUMP is low. 
  
 **Relative Jump TTL (BNC)** **Relative Jump TTL (BNC)**
  
-When asserted HIGH (5 V) while in LOCK mode, RELATIVE JUMP engages a sample-and-hold circuit and takes the Laser Servo out of lock. The voltage on the SERVO OUTPUT is the sample-and-hold value summed in with the LASER JUMP AMPLITUDE. For example, if the laser is locked and the SERVO OUTPUT is -200 mV, then engaging the RELATIVE JUMP and putting 300 mV on the LASER JUMP AMPLITUDE will make the SERVO OUTPUT 100 mV (-200 mV + 300 mV).  This feature is useful for jumping the laser relative to its current lock point (say +200 MHz from a locked transition). When returned to LOW (0 V), the loop filter is reengaged, enabling the laser to be relocked to its original position (by setting LASER JUMP AMP to zero before returning the trigger to TTL low), or to a new lock point (by asserting the trigger low with the LASER JUMP AMP still at a non-zero value). (See [[http://www.vescent.com/jumping-lock-point-d2-125-reconfigurable-servo/|application note here]].) Engaging or disengaging the RELATIVE JUMP is achieved in under 400 μs.+When asserted HIGH (5 V) while in LOCK mode, RELATIVE JUMP engages a sample-and-hold circuit and takes the Laser Servo out of lock. The voltage on the SERVO OUTPUT is the sample-and-hold value summed in with <color black/yellow>the negative</color> of the LASER JUMP AMPLITUDE. For example, if the laser is locked and the SERVO OUTPUT is -200 mV, then putting <color black/yellow>+</color>300 mV on the LASER JUMP AMPLITUDE and engaging the RELATIVE JUMP will set the SERVO OUTPUT to -200 mV + (<color black/yellow>-</color>300 mV) = -500 mV.  This feature is useful for jumping the laser relative to its current lock point (say +200 MHz from a locked transition). When returned to LOW (0 V), the loop filter is reengaged, enabling the laser to be relocked to a new lock point (by asserting the trigger low with the LASER JUMP AMP still at a non-zero value). (See [[http://www.vescent.com/jumping-lock-point-d2-125-reconfigurable-servo/|application note here]].)  Or the laser can be relocked to its original position (by setting LASER JUMP AMP to zero before returning the trigger to TTL low). Engaging or disengaging the RELATIVE JUMP is achieved in under 400 μs.
  
 When asserted HIGH (5V) while in RAMP mode, RELATIVE JUMP applies a DC offset equal to the LASER JUMP AMPLITUDE to the ramp signal at SERVO OUTPUT. When asserted LOW (0V) while in RAMP mode, the ramp signal is DC balanced. When asserted HIGH (5V) while in RAMP mode, RELATIVE JUMP applies a DC offset equal to the LASER JUMP AMPLITUDE to the ramp signal at SERVO OUTPUT. When asserted LOW (0V) while in RAMP mode, the ramp signal is DC balanced.
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 If you are having problems locking the laser, it is a good idea to not use the AUXILIARY SERVO OUTPUT as this complicates the system. Once you get the locking to work properly, you can reconnect this cable. If you are having problems locking the laser, it is a good idea to not use the AUXILIARY SERVO OUTPUT as this complicates the system. Once you get the locking to work properly, you can reconnect this cable.
  
-<imgref factory_settings> shows the nominal corner settings for locking the Vescent D2-100 to atomic spectroscopy.  If all else fails, return to these setting, turn down the gain and try again.+<imgref factory_settings> shows and <tabref factory_setting> lists the nominal corner settings for locking the Vescent D2-100 (or a Photodigm TOSA) to atomic spectroscopy.  If all else fails, return to these setting, turn down the gain and try again.
  
 <WRAP center round box 400px><imgcaption factory_settings|Factory settings for locking a D2-100> <WRAP center round box 400px><imgcaption factory_settings|Factory settings for locking a D2-100>
-{{ {{ d2:d2-125:factory_settings.jpg?direct&400 |}} |}}</imgcaption></WRAP>+{{ {{ d2:d2-125:factory_settings_red.png?direct&700 |}} |}}</imgcaption></WRAP> 
 + 
 +<WRAP center round box 60%><tabcaption factory_setting |D2-125 locking D2-100 or TOSA> 
 +| **Corner**                                                       | **Value**       | **Units** 
 +| First Integrator (high freq.)                                    | low freq.             | 
 +| First Integrator (low freq.)                                     | 10              | Hz         | 
 +| Second Integrator (high freq.)                                   | low freq.             | 
 +| Second Integrator (low freq.)                                    | 500             | Hz         | 
 +| Differential (high freq.)                                        | OFF             | 
 +| Differential (low freq.)                                         | 100              | kHz         | 
 + 
 +</tabcaption></WRAP>
  
  =====D2-125 Stand-alone Test=====  =====D2-125 Stand-alone Test=====
d2/laser_servo.1550764506.txt.gz · Last modified: 2021/08/26 14:26 (external edit)