Vescent D2-105 - User Manual

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2021/12/18 07:41 1/19 Laser Controller

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D2-105 Laser Controller

Laser Controller

Model No. D2-105 / D2-105-500

Document Revision: 4.2

Document Last Updated on 2021/12/17 00:00

Please read Limited Warranty and General Warnings

and Cautions prior to operating the D2-105.

D2-105 web page

Description:

The laser controller has two temperature controllers

capable of sub-mK stability

and a 200 mA or 500 mA

precision current source based on the Libbrecht-Hall

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 range of pole settings for the

T2 temperature control loop

(diode temperature control) for

D2-105 Laser Controllers with

Serial Number 2675 and higher

(Temperature Control Board

Serial Number 6987 and higher)

have been modiﬁed to allow the

user to more easily control a low

thermal mass laser assembly

such as a Photodigm TOSA.

Please use the appropriate

instructions in the “Tuning the

Temperature Controller” section

of this manual for your Laser

Controller and laser type.

Always power down the D2-105

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The Vescent Photonics D2-105 Laser Controller is a sophisticated device designed for precise control of laser diodes, offering high stability and a range of features for demanding applications. It comes in two main models: the D2-105 and the D2-105-500, with the latter supporting higher current output.

Function Description:

The D2-105 Laser Controller integrates two independent temperature controllers and a precision current source. The temperature controllers are capable of sub-mK stability, crucial for maintaining consistent laser performance. The current source, based on the Libbrecht-Hall circuit, provides either 200 mA (D2-105) or 500 mA (D2-105-500) of precision current. A key feature is its ability to facilitate very fast current modulation via a servo input, enabling high-speed servo control of the laser's frequency. This current servo input can handle frequencies over 10 MHz, limited by its 1 kΩ input impedance. Additionally, an RF port is available for even higher frequency modulation, allowing for advanced laser control techniques such as FM sideband generation.

The controller's design emphasizes safety and reliability. It incorporates safety interlocks, including a key switch and a remote interlock, to prevent accidental laser operation. The laser diode is shorted to ground when the laser switch is in the "Off / Reset" position, ensuring safety during connections and maintenance. A "soft start" circuitry in the current source limits the ramp time of the current to the set point to over 300 ms, protecting the laser diode from sudden current surges.

Important Technical Specifications:

Current Source:
- Current Range: 0-200 mA (D2-105), 0-500 mA (D2-105-500)
- Current Noise Density: <100 pA/√Hz (D2-105), <200 pA/√Hz (D2-105-500)
- RMS Noise (10Hz - 100kHz): <50 nA (D2-105), <100 nA (D2-105-500)
- RMS Noise (10Hz - 1MHz): <100 nA (D2-105), <150 nA (D2-105-500)
- RMS Noise (10Hz - 10MHz): <300 nA (D2-105), <500 nA (D2-105-500)
- Monitor Resolution (Display): 0.1 mA (D2-105), 1 mA (D2-105-500)
- Absolute Accuracy: 2%
- Temperature Coefficient: <1 µA/°C (D2-105), <5 µA/°C (D2-105-500)
Current Servo Input:
- Input Impedance: 1000 Ω
- Bandwidth: >10 MHz
- Modulation Coefficient: 1 mA/V
- Servo Input Modulation Range: ±10 V
RF Input Bandwidth: 0.5 - TBD MHz
Temperature Servo Input:
- Input Impedance: 100 kΩ
- Temp Modulation Coefficient (Low/High Gain): 95 mK/V / 9,000 mK/V
Temperature Control:
- Temperature Setpoint Range: 1-50 °C
- Long Term Stability (T2): ~1 mK/day
- Max TEC Current (Voltage): 1 A (4 V)
- Calibrated to Analog Technologies ATH10KR8 Thermistor (10k Ω, Beta 3480 K, T₀ 25 °C)
Environmental Conditions:
- Operating Temperature: >15°C and <30°C
- Humidity: <60%
- Dew Points: <15°C

Usage Features:

The D2-105 features a user-friendly front panel with a 3½ digit display and a selector knob to monitor various signals, including current, current limit, housing temperature set, housing temperature error, laser temperature set, and laser temperature error. An LED indicator below the display shows the currently displayed signal and its units.

Current Control: Fine and coarse current adjustments allow precise setting of the laser diode injection current. A trimpot for "Current Limit Set" ensures the laser current does not exceed a safe maximum. The "Current Lim" LED indicates when the current limit circuit is active.
Servo and RF Inputs: Dedicated BNC connectors for "Current Servo Input" and "RF Input" enable external modulation and high-speed frequency control. The current servo input adds or subtracts current with a modulation coefficient of 1 mA/V, while the RF input is AC coupled for high-frequency modulation.
Temperature Control: Two independent temperature control loops (T1 for housing, T2 for laser diode) provide robust temperature stabilization. The T2 setpoint is adjustable from the front panel, while T1 is adjusted via a side-panel trimpot. A "Temp Servo Input" allows external control of the T2 setpoint, with selectable "Low" and "High" gain modes for different tuning sensitivities.
Safety Interlocks: A key-switch and a remote interlock BNC ensure the laser can only be turned on under safe conditions. The "Laser ON-Off/Reset" switch provides a manual reset function for the interlocks and controls the laser's power state. The "Laser On" LED indicates when the laser is about to turn on (after a 5-second delay).
Power I/O: Power is supplied via a 9-pin D-sub connector, with pin-outs clearly defined for +15V, -15V, +5V, and returns. The device is designed for operation in a laboratory environment.

Maintenance Features:

Tuning the Temperature Controller: The manual provides detailed instructions for tuning the temperature servo response to match the thermal load of the laser module. This involves adjusting pole settings and gain via trimpots and click-switches located on the right side panel (which requires removal for access). The Ziegler-Nichols tuning method is recommended.
Troubleshooting: The manual offers guidance for common issues, such as the "Laser ON" LED not turning on (checking interlocks, COARSE CURRENT knob, and laser diode connection) and oscillations in temperature loops (reducing gain or increasing time-constants).
UPS Considerations: For uninterrupted power, users are advised to select a UPS model that provides a sine wave voltage profile to avoid potential damage from high-frequency components of modified square wave profiles, which can interact poorly with Vescent modules.
Power Supply Placement: To minimize noise, the D2-005 power supply should be placed at least 18 inches (45cm) away from other electronics or rotated 90° to prevent radiation of mains electricity noise.

The D2-105 Laser Controller is a comprehensive solution for researchers and engineers requiring precise and stable control over laser diodes, with robust safety features and detailed tuning capabilities to optimize performance for various thermal loads.

Vescent D2-105 Specifications

General

Brand	Vescent
Model	D2-105
Category	Controller
Language	English