The Newport / New Focus 3501 Optical Chopper Controller delivers precision light modulation for optical experiments requiring stable, jitter-free chopping frequencies. A crystal-controlled frequency synthesizer generates internal reference signals from 4 Hz to 6.4 kHz, while an external Sync Input enables locking to outside sources for noise reduction and signal processing. The controller supports harmonic chopping (2 to 15×) and subharmonic operation (1/2 to 1/15×), with a phase shifter providing −180 to +179° variation relative to the reference. Active motor stabilization via photo-sensor feedback maintains chopper head frequency accuracy across single and dual beam configurations.
Technical Specifications
• Chopping Frequency Range: 4 Hz to 6.4 kHz
• Harmonic Chopping: 2 to 15× reference frequency
• Subharmonic Chopping: 1/2 to 1/15× reference frequency
• Phase Control: −180 to +179° phase shift relative to reference
• Frequency Stabilization: Crystal-controlled synthesizer with photo-sensor feedback and active motor speed control
• Motor: High-quality DC motor with integrated photo-sensor for frequency monitoring
• Output Signals: TTL-level outputs for lock-in amplifier triggering; sum and difference outputs from inner and outer wheel frequencies for nonlinear optics applications
• Chopper Wheels: Four wheels included; additional photo-etched wheels available separately (2-slot, 7/5-slot, 42/30-slot, 60-slot configurations)
– Key Features
• GPIB (IEEE-488) interface for remote control of all functions
• External synchronization input for integration with complex experimental setups
• High-stability phase shifter enabling precise temporal alignment
• Flexible mounting: 1/2-inch post, optical bench bolting (1/4-20 or M6), or rotatable breadboard base
• Model 3510 Rack Mount Kit available for 19-inch rack installation
– Typical Applications
• Synchronous signal detection and lock-in amplification
• Nonlinear optical experiments requiring harmonic and subharmonic generation
• Low-noise optical measurement systems
• Multi-beam interference and phase-modulated spectroscopy
– Compatibility & Integration
The 3501 integrates into optical benches and laboratory racks. GPIB connectivity and Sync Input allow automated control and tight synchronization with external instruments. Supplied with four chopper wheels and protective wheel cover.
