The Model 3700 Temperature Controller provides a 336 W bipolar output for operation with thermoelectric (TE) coolers. At the unit's heart, DSP based controls allow for PID settings with fast settling times. This feature combined with sound electronics design and quality components results in great temperature stability and higher reliability.
One hour temperature stability measurements performed in a typical lab environment, on a Newport laser Mount 764H-110 with an Oclaro BW-series laser running at 10W optical output power. Ambient temperature variations during the test period of the order of 2 °C is shown. The Laser mount temperature was set at 21 °C for the entire test over a 1 hour period and was held stable at 21 °C with a variation of ± 0.0004 °C over the 1 hour period.
24 hour temperature stability measurements were performed in a typical lab environment, on a Newport Laser Mount 764H-110 with an Oclaro BW-series laser running at 10W optical output power. The graph displays ambient temperature variations during the test period of the order of 3 °C. The laser mount temperature was set to 21 °C with a variation of ± 0.00077 °C over the 24 hour period.
PID control is implemented in the Model 3700 that meets all the temperature stabilization requirements for laser diode users. During operation, the front panel controls can be disabled to prevent any changes in the output by accidental misadjustment of the control knob. Protection features include: ITE Limit, Hi and Lo Temperature Limits, Voltage Limits, Sensor Open and TE Open Detection. To prevent noise pickup, either by the output lines or the sensor inputs — resulting in undesirable temperature oscillations — shielded cables are also available.
Innovative hardware and firmware design allows 3700 to output 14 A over the full 0-24 V compliance range. Compare this with our competitors’ controllers output capability shown.
All standard temperature sensors including thermistors, platinum RTD, AD590/592 and LM335 IC sensors are supported without the need for additional interface units. Sensor calibration constants are easily programmed for direct readout in ° C.
All pertinent TE cooler parameters ITE, VTE, temperature sensor (° C, R, Amp, or Volts) are measured and simultaneously presented on the four line alphanumeric LCD display.
The above figure figure shows that the threshold current and differential responsivity of a laser diode are strongly affected by the laser’s temperature. The laser threshold will increase exponentially with temperature as exp(T/T0), where T is the laser temperature and T0 is the “characteristic temperature” of the laser (typically between 60 to 150°C). T0 is a measure of the temperature sensitivity of the device with higher values implying that the device is more thermally stable. T0 is an important laser diode characteristic and is commonly extracted from multiple L-I curves. Changes in temperature also affect the bandgap of the semiconductor junction and therefore, the peak wavelength of the gain profile. This results in a linear relationship between temperature and the center wavelength of the laser diode (see above figure) with typical temperature tuning coefficients of 0.3 nm/°C. As a result, a temperature controller plays a key role in determining the laser wavelength. Please see Fundamentals of Laser Diode Control for additional information.
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