Low noise butterfly laser diode controller
Koheron CTL100 is a low noise current driver with modulation combined with a temperature controller. It is designed to drive narrow-linewidth laser diodes in Type 2 butterfly package. It is compatible with floating diodes, which means that neither the anode nor the cathode should be connected to the case. It drives up to 400 mA laser current with a current noise density of only 450 pA/√Hz. The CTL100 fits in a 75 mm x 75 mm square, uses a single 5 V supply, and can operate between 0 and 50°C. The CTL100 is conduction-cooled. It comes with an aluminum base plate and a zero insertion force socket for easy mounting.
|Laser current||5 mA to 400 mA||5 mA to 400 mA|
|Compliance voltage||2.3 V||2.3 V|
|RMS noise(10 Hz to 1 MHz, M modulation gain)||386 nArms||510 nArms|
|Current noise density(1 kHz)||450 pA/√Hz||450 pA/√Hz|
|1/f corner noise||20 Hz||20 Hz|
|Temperature coefficient||15 ppm/°C||15 ppm/°C|
|Current limit||420 mA||420 mA|
|Slow start(90 % setpoint)||1000 ms||1000 ms|
|Modulation gain(L setting)||2 mA/V||2 mA/V|
|Modulation gain(M setting)||20 mA/V||20 mA/V|
|Modulation gain(H setting)||200 mA/V||200 mA/V|
|3 dB modulation bandwidth||150 kHz||11 MHz|
|AC modulation cutoff frequency||70 kHz||1.5 MHz|
|Maximum current||1.2 A||1.2 A|
|Temperature range(10 K thermistor)||12 °C to 25 °C||12 °C to 25 °C|
|Compliance voltage||3.4 V when cooling, 0.7 V when heating||3.4 V when cooling, 0.7 V when heating|
|Temperature stability||0.0015 °C/°C||0.0015 °C/°C|
|Laser power monitor|
|Photodiode current||0 mA to 1 mA||0 mA to 1 mA|
|Gain||3.9 V/mA||3.9 V/mA|
|Bandwidth||50 MHz||50 MHz|
|Outside dimensions||75 mm x 85 mm x 27 mm||75 mm x 85 mm x 27 mm|
|Weight||103 g||103 g|
|Supply voltage||4.9 V to 5.5 V||4.9 V to 5.5 V|
|Operating temperature||0 °C to 50 °C||0 °C to 50 °C|
|Compatible lasers||Type 2, Floating diodes / anode-grounded||Type 2, Floating diodes / anode-grounded|
More Laser drivers
Current stability is depicted in the following figure showing a 24-hour long evolution of current, set to 350 mA at 25 °C ambient temperature. After a 2 h warm-up time, current is stable within ±5 ppm.
The figure below show the evolution of the CTL100 current, set at 350 mA, measured with a Keysight 34470A digital multimeter across a 5 Ω resistor.
The figure below shows the current variation for different ambient temperatures between 5 and 55 °C. Temperature coefficient is below 15 ppm/°C.
DC current modulation input
A modulation input from DC to 100 kHz is available (10 MHz for the CTL100-A-400).
A jumper allows to choose between 3 modulation gains (2 mA/V, 20 mA/V or 200 mA/V).
AC modulation input
An AC modulation input using a bias-tee is available for modulation frequencies above 100 kHz for the 100 kHz bandwidth version (A-400) and above 3 MHz for the 10 MHz bandwidth version (B-400). The actual modulation gain depends on the value of the resistor integrated in the laser.
The power spectral density of the 100 kHz bandwidth version (A-400) current noise was characterized for the 3 modulation gains.
Current noise integrated between 10 Hz and 1 MHz is 385 nA, 386 nA and 406 nA RMS at the low, medium and high gain settings respectively.
The temperature controller consists of a precision Wheatstone bridge, an analog PID controller and a linear current driving stage. PID gains are fixed and have been adjusted for a typical butterfly laser diode. Temperature setpoint is adjusted with an ultra high precision trimming potentiometer.