ILX Lightwave LDC-3714B 50/100 mA Precision Laser Diode Controller with 16 W TEC

ILX Lightwave LDC-3714B Precision Laser Diode Controller

The ILX Lightwave LDC-3714B is a high-precision, microprocessor-based laser diode controller designed specifically for very low-power laser diodes. It combines a dual-range 50/100 mA laser diode current source and a 16 W thermoelectric temperature controller in one benchtop instrument, providing coordinated electrical and thermal control for sensitive laser devices.

The laser current source offers low noise, high stability, adjustable compliance voltage, monitor-photodiode feedback, and external analog modulation. The integrated TEC controller supplies a low-noise bipolar output and supports thermistors, AD590 and LM335 integrated-circuit temperature sensors, and compatible RTD sensors when the required converter is used.

The LDC-3714B supports local operation through separate LASER and TEC front-panel sections and remote operation through its standard GPIB/IEEE-488.2 interface. Instrument settings can be stored in ten memory locations, while calibration information is retained in nonvolatile memory. These functions make the controller suitable for laser diode characterization, photonics research, production testing, burn-in stations, optical component development, and automated laboratory systems.

Features and Benefits of the ILX Lightwave LDC-3714B

• Designed for very low-power laser diodes: Provides dual current ranges of 0 to 50 mA and 0 to 100 mA for precise control of sensitive devices.
• Integrated laser and temperature control: Combines a laser diode current source and 16 W TEC controller in one instrument.
• Three laser operating modes: Supports constant-current CW, constant-current high-bandwidth, and constant optical power operation.
• Low-noise current output: Provides less than 1.5 µA RMS noise in both current ranges under the documented test conditions.
• High current stability: Offers short-term stability below 20 ppm and long-term stability below 40 ppm under the specified conditions.
• Adjustable compliance voltage: Allows the laser drive compliance limit to be set from 0 V to 10 V.
• Analog modulation: Supports external current modulation from DC to 1 MHz in high-bandwidth mode.
• Constant optical power control: Uses monitor-photodiode feedback to regulate laser output power.
• 16 W bipolar TEC output: Provides heating and cooling control with up to ±4 A of TE current.
• Multiple temperature-control modes: Supports constant temperature, constant sensor value, and constant TE current.
• Broad sensor compatibility: Works with compatible NTC thermistors, AD590 sensors, LM335 sensors, and supported RTDs.
• Laser protection functions: Includes a keyswitch, interlock, output delay, current limit, compliance limit, temperature limit, and rapid output shutdown.
• Ten setup memories: Saves and recalls complete front-panel configurations for repeatable testing.
• GPIB automation: Supports IEEE-488.2 remote operation and compatible LabVIEW instrument control.

Dual-Range 50/100 mA Laser Current Source

The LDC-3714B provides two laser drive current ranges for controlling low-current laser diodes. The 50 mA range offers finer adjustment for especially sensitive devices, while the 100 mA range provides additional current capacity for compatible laser diode packages.

The 0 to 50 mA range provides 1 µA setpoint resolution. The 0 to 100 mA range provides 2 µA setpoint resolution. Setpoint accuracy is specified at ±0.05% of full scale in both ranges.

The current range should be selected according to the operating current and maximum rating of the connected laser diode. Using the lowest range that fully accommodates the required drive current provides the finest available setpoint resolution.

Constant-Current CW Mode

Constant-current CW mode is optimized for stable direct-current operation. It provides low noise and enhanced laser protection for applications that do not require high-frequency current modulation.

This mode is suitable for laser diode characterization, wavelength testing, optical power measurements, source stabilization, burn-in evaluation, and other applications requiring steady laser current.

The low-bandwidth current response extends from DC to 15 kHz. External modulation remains available, but the limited bandwidth helps reduce unwanted noise and high-frequency disturbances.

High-Bandwidth Current Mode

The high-bandwidth constant-current mode supports external analog modulation from DC to 1 MHz. This capability is useful for dithering the laser current, tuning optical power or wavelength, investigating dynamic response, and integrating the controller into modulated laboratory test systems.

The external modulation input is implemented as a differential instrumentation-amplifier input. This arrangement allows the modulation control signal and laser output circuit to use different grounds, supporting more flexible test-system integration.

The modulation input accepts 0 V to 10 V with a nominal input impedance of 10 kO. The transfer function is 5 mA/V in the 50 mA range and 10 mA/V in the 100 mA range.

Constant Optical Power Mode

The LDC-3714B supports constant optical power operation using feedback from a laser diode rear-facet monitor photodiode or a compatible external photodiode. The controller adjusts laser drive current to maintain the selected optical power or monitor current.

The photodiode input uses a differential configuration and supports a feedback-current range from 5 µA to 5000 µA. Adjustable photodiode reverse bias from 0 V to 5 V supports different photodiode configurations.

Photodiode output stability is specified at 0.02% over the documented interval, assuming no change in detector responsivity. Setpoint accuracy is ±0.05% of full scale.

A user-defined photodiode responsivity value can be entered so the controller can calculate and display optical power. The displayed value depends on the accuracy of the entered responsivity and the stability of the monitor photodiode.

Low Noise and High Stability

In the 50 mA and 100 mA ranges, current-source noise and ripple are specified below 1.5 µA RMS in both high-bandwidth and low-bandwidth modes under the documented optical test conditions.

The current temperature coefficient is below 50 ppm/°C. Short-term current stability is below 20 ppm over one hour, while long-term stability is below 40 ppm over 24 hours under the documented half-scale conditions.

These characteristics support precision laser diode testing where current noise and drift can influence optical power, wavelength, linewidth, or measurement repeatability.

Adjustable Compliance Voltage

The laser current-source compliance voltage can be adjusted from 0 V to 10 V. Setting the compliance limit close to the voltage required by the connected laser diode helps prevent excessive voltage from being applied during abnormal conditions.

Compliance-voltage adjustment resolution is 50 mV, with specified accuracy of ±2.5%. The selected limit should provide enough voltage for normal laser operation while remaining below the maximum safe level for the device and test fixture.

The laser forward voltage can be displayed from 0.000 V to 10.000 V with 1 mV resolution. Accuracy is specified at ±2 mV under the documented four-wire measurement conditions while driving a calibration load.

Adjustable Laser Current Limit

The current limit provides an independent upper boundary for laser drive current. In the 50 mA range, the limit can be set from 1 mA to 50.5 mA with 0.25 mA resolution. In the 100 mA range, it can be set from 1 mA to 101 mA with 0.5 mA resolution.

Current-limit accuracy is ±0.5 mA in the 50 mA range and ±1 mA in the 100 mA range. The limit should be established before the laser output is enabled and should remain below the maximum safe operating current of the connected device.

Integrated 16 W TEC Controller

The LDC-3714B includes a bipolar thermoelectric controller capable of both heating and cooling. It provides up to 4 A of TE current, more than 4 V DC compliance, and a maximum output power of 16 W into the documented load.

The TEC controller uses a Smart Integrator Hybrid PI control algorithm to maintain the selected temperature, sensor value, or TE current. Current noise and ripple are specified below 1 mA RMS under the documented conditions.

A fully independent hardware current limit prevents TE current from exceeding the selected boundary. The current limit can be set from 0 A to 4 A with ±50 mA setpoint accuracy.

Temperature-Control Operating Modes

The integrated TEC section supports three control modes:

• Constant temperature: Maintains a selected temperature using a compatible thermistor or integrated-circuit sensor.
• Constant sensor value: Maintains a selected thermistor resistance, AD590 current, or LM335 voltage.
• Constant TE current: Drives the thermoelectric module at a selected current level.

The software temperature range extends from -99.9 °C to 199.9 °C. The actual achievable temperature depends on the TE module, thermal load, heatsinking, ambient conditions, sensor, laser diode mount, and user-defined controller configuration.

Temperature Sensor Compatibility

The LDC-3714B supports compatible two-wire NTC thermistors with usable resistance from 25 O to 450,000 O. Thermistor sensing currents of 10 µA and 100 µA are available.

The controller also supports AD590 and LM335 integrated-circuit temperature sensors. The AD590 is operated with an 8 V sensor bias, while the LM335 uses a 1 mA bias.

Compatible 100 O RTD sensors can be used when the required TSC-599 RTD Temperature Sensor Converter is installed. Sensor selection and calibration must match the actual device connected to the controller.

Temperature Accuracy and Stability

With a typical 10 kO thermistor and the documented configuration, temperature setpoint accuracy is specified at ±0.2 °C over the listed -20 °C to 50 °C intervals. Resolution is 0.1 °C from -20 °C to 20 °C and 0.2 °C from 20 °C to 50 °C.

AD590 and LM335 temperature setpoints cover -20 °C to 50 °C with 0.01 °C resolution and ±0.1 °C accuracy under the documented conditions.

Short-term temperature stability is ±0.004 °C or better over one hour, while long-term stability is ±0.01 °C over 24 hours under the stated test conditions.

Actual accuracy and stability depend on the sensor, calibration, thermal load, mount, controller settings, cable resistance, airflow, ambient conditions, and quality of the thermal interface.

Temperature Measurement and TEC Monitoring

Temperature can be displayed from -99.9 °C to 199.9 °C with 0.01 °C resolution. Using a 10 kO thermistor at the 10 µA setting, documented measurement accuracy is ±0.1 °C under the specified conditions. At the 100 µA setting, it is ±0.05 °C.

Thermistor resistance can be displayed from 0.00 kO to 450.00 kO at the 10 µA setting and from 0.000 kO to 45.000 kO at the 100 µA setting.

TE current is displayed from -4.000 A to +4.000 A with 0.001 A resolution and ±0.04 A accuracy. TEC voltage can be measured remotely through GPIB over a -10.0 V to +10.0 V range with 1 mV resolution and ±30 mV documented accuracy.

Laser Diode Protection

The LDC-3714B includes several protection functions intended to reduce the risk of damage to sensitive laser diodes and thermoelectric assemblies.

• Keyswitch: Restricts activation of the laser output.
• Interlock: Supports integration with external safety and fixture circuits.
• Output delay: Delays current application during output activation.
• Current limit: Prevents the selected laser current boundary from being exceeded.
• Compliance-voltage limit: Restricts the voltage available from the laser drive circuit.
• High-temperature limit: Protects the controlled device from excessive temperature.
• Fast output shutdown: Provides rapid current removal under supported fault conditions.
• Sensor and TEC fault response: Shuts down laser output if the temperature sensor or TE module opens during operation.

The safety design includes a keyswitch, interlock, and output delay intended to meet the documented CDRH requirements of US 21 CFR 1040.10.

Transient Protection

The maximum operational current transient is specified below 2 mA for both LDC-3714B current ranges. This specification covers normal and accidental events such as power switching, current-output switching, and removal of the power-line connection.

For the documented 1 kV electrical fast-transient test, maximum current transient is below 5 mA. During the documented surge test, maximum transient is below 8 mA.

These protection characteristics help reduce potentially damaging current excursions during switching and power-line disturbances. Correct cabling, grounding, interlocking, current limiting, and test-fixture design remain essential.

Front-Panel Operation

The front panel is divided into separate LASER and TEC control sections. Each section uses a five-digit green LED display, providing clear visibility of current, optical power, forward voltage, temperature, resistance, TE current, and related operating parameters.

A digital adjustment knob supports precise parameter entry. Status and fault indicators help identify operating limits, interlock conditions, sensor faults, and other protective states.

The current-source and temperature-control electronics are electrically isolated, allowing the controller to support different grounding and test-fixture configurations.

Save and Recall Functions

The LDC-3714B provides ten nonvolatile memory locations for storing instrument configurations. The SAVE function records the selected front-panel settings, while RECALL restores a stored configuration for repeated measurements.

Setup memory is useful when one controller is used with several laser diode packages, operating currents, temperature sensors, or test procedures. Each configuration should be verified before the laser output is enabled because the recalled limits may not be appropriate for every device.

Closed-Case Calibration

The LDC-3700B architecture supports calibration through the front panel or GPIB interface without opening the instrument enclosure. Calibration data is stored automatically in nonvolatile memory.

This design simplifies routine maintenance and reduces the need to access internal circuits during adjustment. Suitable calibrated standards, loads, thermistor simulators, current measurement equipment, and voltage measurement equipment are required for formal calibration.

GPIB and Automated Test Integration

The LDC-3714B includes a standard GPIB/IEEE-488.2 interface using a 24-pin IEEE-488.1 connector. Remote operation allows compatible software to configure laser current, TEC settings, limits, modes, measurements, and other supported functions.

LabVIEW instrument drivers were offered for the LDC-3700B Series. This allows the controller to be integrated into automated characterization systems, production stations, reliability tests, temperature sweeps, wavelength measurements, and optical power experiments.

The trigger output provides a TTL signal with a documented pulse width of 13 µs and a delay of 12 ms for coordination with compatible external measurement equipment.

Typical Applications

• Very low-power laser diode characterization
• Laser diode current and temperature control
• Laser wavelength stabilization
• Optical power stabilization
• Laser diode burn-in and reliability testing
• Photonic component research and development
• External current modulation and laser dithering
• Laser diode production testing
• Temperature-dependent optical measurements
• Automated GPIB laboratory systems
• University and research laboratory experiments
• Semiconductor laser evaluation

Product Overview

Brand	ILX Lightwave
Model	LDC-3714B
Product Series	LDC-3700B Series
Product Category	Precision Laser Diode Current and Temperature Controller
Laser Current Ranges	0 to 50 mA and 0 to 100 mA
TEC Output	16 W maximum, bipolar
Remote Interface	GPIB/IEEE-488.2
Primary Application	Precision control and characterization of very low-power laser diodes

 

Laser Current Source Specifications

Specification	50 mA Range	100 mA Range
Output Current Range	0 to 50 mA	0 to 100 mA
Setpoint Resolution	1 µA	2 µA
Setpoint Accuracy	±0.05% of full scale	±0.05% of full scale
Compliance Voltage	0 V to 10 V adjustable	0 V to 10 V adjustable
Temperature Coefficient	Less than 50 ppm/°C	Less than 50 ppm/°C
One-Hour Stability	Less than 20 ppm	Less than 20 ppm
24-Hour Stability	Less than 40 ppm	Less than 40 ppm
High-Bandwidth Noise and Ripple	Less than 1.5 µA RMS	Less than 1.5 µA RMS
Low-Bandwidth Noise and Ripple	Less than 1.5 µA RMS	Less than 1.5 µA RMS

 

Laser Protection and Limit Specifications

Specification	50 mA Range	100 mA Range
Compliance Adjustment Range	0 V to 10 V	0 V to 10 V
Compliance Adjustment Resolution	50 mV	50 mV
Compliance Adjustment Accuracy	±2.5%	±2.5%
Current-Limit Range	1 mA to 50.5 mA	1 mA to 101 mA
Current-Limit Resolution	0.25 mA	0.5 mA
Current-Limit Accuracy	±0.5 mA	±1 mA
Operational Current Transient	Less than 2 mA	Less than 2 mA
1 kV EFT Current Transient	Less than 5 mA	Less than 5 mA
Surge Current Transient	Less than 8 mA	Less than 8 mA

 

Photodiode Feedback Specifications

Specification	Details
Feedback Type	Differential
Photodiode Reverse Bias	0 V to 5 V adjustable
Photodiode Current Range	5 µA to 5000 µA
Output Stability	0.02% under the documented conditions
Setpoint Accuracy	±0.05% of full scale
Displayed Photodiode Current Range	0 µA to 5000 µA
Displayed Photodiode Resolution	1 µA
Displayed Photodiode Accuracy	±2 µA
User-Defined Responsivity Range	0.00 to 1000.00 µA/mW
Responsivity Resolution	0.01 µA/mW

 

External Modulation and Trigger Specifications

Specification	50 mA Range	100 mA Range
Modulation Input	0 V to 10 V, 10 kO	0 V to 10 V, 10 kO
Transfer Function	5 mA/V	10 mA/V
High-Bandwidth Response	DC to 1 MHz	DC to 1 MHz
Low-Bandwidth Response	DC to 15 kHz	DC to 15 kHz
Trigger Output Type	TTL	TTL
Trigger Pulse Width	13 µs	13 µs
Trigger Delay	12 ms	12 ms

 

Laser Measurement Display Specifications

Specification	50 mA Range	100 mA Range
Displayed Output Current	0 to 50.000 mA	0 to 100.00 mA
Output Current Resolution	0.001 mA	0.002 mA
Output Current Accuracy	±0.05% of full scale	±0.05% of full scale
Displayed Optical Power Range	0.00 mW to 101.00 mW	0.00 mW to 101.00 mW
Optical Power Resolution	0.01 mW	0.01 mW
Forward Voltage Range	0.000 V to 10.000 V	0.000 V to 10.000 V
Forward Voltage Resolution	1 mV	1 mV
Forward Voltage Accuracy	±2 mV under the documented conditions	±2 mV under the documented conditions

 

TEC Output Specifications

Specification	Details
Output Type	Bipolar constant-current source
Compliance Voltage	Greater than 4 V DC
Maximum Output Current	4.0 A
Maximum Output Power	16 W
Current Noise and Ripple	Less than 1 mA RMS under the documented conditions
Current-Limit Range	0 A to 4 A
Current-Limit Setpoint Accuracy	±50 mA
Control Algorithm	Smart Integrator Hybrid PI

 

Temperature Control Specifications

Specification	Details
Software Temperature Range	-99.9 °C to 199.9 °C
Thermistor Setpoint Resolution from -20 °C to 20 °C	0.1 °C
Thermistor Setpoint Resolution from 20 °C to 50 °C	0.2 °C
Thermistor Setpoint Accuracy	±0.2 °C under the documented conditions
AD590 and LM335 Setpoint Range	-20 °C to 50 °C
AD590 and LM335 Setpoint Resolution	0.01 °C
AD590 and LM335 Setpoint Accuracy	±0.1 °C under the documented conditions
One-Hour Temperature Stability	±0.004 °C or better
24-Hour Temperature Stability	±0.01 °C

 

Temperature Sensor Specifications

Specification	Details
Thermistor Type	Two-wire NTC thermistor
IC Temperature Sensors	AD590 and LM335
RTD Support	Pt100 or compatible 100 O RTD using the TSC-599 converter
Thermistor Sensing Currents	10 µA and 100 µA
Usable Thermistor Range	25 O to 450,000 O
AD590 Bias	8 V
LM335 Bias	1 mA
Thermistor User Calibration	Steinhart-Hart
IC Sensor and RTD User Calibration	Two-point calibration

 

Display and Connector Specifications

Specification	Details
Laser Display	Five-digit green LED
TEC Display	Five-digit green LED
Laser Drive Connector	9-pin D-sub
TEC Control Connector	15-pin D-sub
External Modulation Connector	Coaxial BNC instrumentation-amplifier input
GPIB Connector	24-pin IEEE-488.1
Chassis Ground	4 mm banana jack

 

Physical and Environmental Specifications

Specification	Details
Dimensions	353 mm x 345 mm x 127 mm
Weight	Approximately 10.2 kg or 22.5 lb
Operating Temperature	0 °C to 50 °C
Storage Temperature	-40 °C to 70 °C
Humidity	Less than 90% relative humidity, non-condensing
Power Requirements	110 V to 115 V AC or 220 V to 240 V AC, 50 Hz to 60 Hz
Line Voltage Tolerance	+6%/-10%

 

Compatible Accessories

Accessory	Application
CC-305S	Current-source to laser diode mount interconnect cable
CC-306S	Current-source to unterminated interconnect cable
CC-501S	TE controller to unterminated interconnect cable
CC-505S	TE controller to laser diode mount interconnect cable
LNF-320	Low-noise filter
TS-510	Calibrated 10 kO thermistor
TS-520	Uncalibrated 10 kO thermistor
TS-523	Uncalibrated 20 kO thermistor
TS-525	Uncalibrated 100 k