The temperature controller maintains the nonlinear crystal at a stable temperature to ensure optimal phase matching for SPDC. The target temperature can be adjusted based on the input laser wavelength. Reaching thermal equilibrium typically takes several minutes, depending on the ambient conditions and the required temperature offset.
Description: This parameter sets the temperature range over which the controller output transitions linearly from -100% to +100%, centered around the setpoint. A smaller bandwidth results in a higher gain and faster response, while a larger bandwidth provides slower, more stable behavior.
Tuning Tip: The proportional bandwidth is inversely related to gain. Reducing the bandwidth increases sensitivity and responsiveness but may also increase overshoot or instability.
Description: With proportional control alone, the controller’s output drops to 0% once the actual temperature reaches the setpoint. However, thermal systems typically require a non-zero output to maintain the setpoint. The integral term corrects this by adding power based on the cumulative temperature error over time, ensuring accurate long-term stability.
Tuning Tip: Higher integral gain accelerates error correction but may cause oscillation. Increase cautiously and test for stability.
Description: The derivative term responds to the rate of temperature change, allowing the controller to anticipate power adjustments in response to rapid thermal fluctuations. It is particularly useful for systems with large thermal lag or for minimizing overshoot.
Tuning Tip: Use derivative gain when the system is slow to respond or prone to temperature overshoots. Start low and increase only as needed.