1. CAVITY LOCK ELECTRONICS Dan Sexton, Sirish Nanda, and Abdurahim Rakhman

2. Design Goals Lock-In on Cavity Resonance Slow and Fast Laser Frequency Scan Slow and Fast Error Compensation Incorporate on board micro-controller Compatible with Stanford Research SIM900 Crate

3. Pound-Drever-Hall Locking Scheme Photo detector Beam Splitter Cavity Oscillator Phase Shifter Mixer Low Pass Filter 0 Tunable Laser PID- Regulator Error signal Detect phase of the resonance from reflected light Feedback to tunable element to stay locked to resonance Keep the cavity resonate forever It is very hard to stabilize the cavity length in nm level System Schematic

4. Electronics Overview Slow and Fast Laser Frequency Scan Search for Signal of Interest Slow Scan Rate – 0.01 Hz – 1Hz Fast Scan Rate – 3 Hz – 30Hz External Modulation 10-30 mV @ 1MHz Signal Error Input and Output Polarity Selection (+/-)

5. Electronics Overview (contd) Slow and Fast Error Feedback Integration and Gain Control Loops (PI) Gain Range – x0.1 – x1 Integration Time – 1mS – 10mS Optional Features Trigger Monitor or Input Threshold Monitor or Input

6. Electronics Overview (contd) Analog Devices ADuC-70xx series Micro-Controller 32-Bit 44MHz ARM processor 8 ADC CHs and 4 DAC CHs Drop in module in two different packages Option A – OLIMEX Evaluation Card ADuC-7026 (3 x 3) Option B – OLIMEX DIP Socket ADuC-7020 (1 x 2)

7. Electronics Overview (contd) Stanford Research SIM900 Crate Off the shelf Modular System GPIB and RS-232 interface Regulated Power Supply

8. More Electronics Overview

10. Current Status PCB and enclosure in hand and assembled Bench Testing completed In System Calibration Beginning