ThorLabs Optical Chopper System, Includes Controller, Chopper Head, and Dual-Frequency Blade. PN: MC2000B

The MC2000B Optical Chopper is a precision instrument that utilizes advanced features to modulate light from a continuous beam. The controller uses a phase-locked loop (PLL) motor speed control design to precisely maintain the chopping speed and phase relative to a reference signal. An internal, crystal-stabilized, frequency synthesizer provides an accurate and stable reference frequency for stable long-term performance. The MC2000B Chopper offers faster locking times, interface improvements, and a larger selection of blades than our previous-generation MC2000 Optical Chopper.

An optical switch is used to get the reference signal when the chopper blades pass through and interrupt the beam path. The switch incorporates an LED with a wavelength range of 850 nm - 940 nm that is operated at the 15 mA threshold current to minimize light output from the LED.

Unlike conventional, open-loop speed control designs, the PLL speed control circuit also allows the MC2000B chopper to be synchronized to external reference signals, including other MC2000B choppers and reference sources such as DSP lock-in amplifiers. Please see the Operations tab for more details on the MC2000B chopper and its applications.

The MC2000B design features a high quality, rare earth magnet, DC motor. The photo-etched optical chopper wheel blade is made of 0.01" thick blued clock spring steel for high precision. The compact optical head has a wide base for extra stability, and the base is slotted for two 1/4"-20 (M6) mounting screws on 3" (76.2 mm) centers. The mounting slots have a 1.5" (38.1 mm) radius. The interface cable uses circular snap-on Hirose connectors for easy setup.

The MC2000B controller includes a 240 x 128 pixel graphics display for setting and monitoring chopper functionality. All of the functions are accessible through a front panel control knob with turn and push control. Multiple user setups can be easily saved and recalled from non-volatile memory. A USB interface is included as a standard feature for remote PC control of the MC2000B.

Technical Specifications:

• 20 Hz - 10kHz Chopping Frequency (with default blade)
• < 20 ppm/°C Frequency Drift
• 0.1 Hz Frequency Resolution
• Zero Gauss chamber for checking and correcting probe offset
• Full-range calibration on the 0.1 T, 0.5 T, 3 T, and 20 T ranges
• 20 T measurement range calibrated up to 3 T

Features:

• Crystal-Stabilized, Phase-Locked Feedback Loop Suppresses Low Frequency Drift and Phase Jitter
• Harmonic, Subharmonic, and Fractional Harmonic Chopping with Sum and Difference Reference Outputs
• Microprocessor Controlled
• Single- and Dual-Frequency Blades Available
• Harmonic Frequency Blades Available for Pump-Probe and Other Nonlinear Experiments
• Save and Recall User Setups in Non-Volatile RAM
• USB Interface