CAVITY LOCK ELECTRONICS Dan Sexton Sirish Nanda and

Design Goals n Lock-In on Cavity Resonance n n Slow and Fast Laser Frequency

System Schematic ● Keep the cavity resonate forever Beam Splitter Tunable Laser Cavity It

Electronics Overview n Slow and Fast Laser Frequency Scan n Search for Signal of

Electronics Overview (cont’d) n Slow and Fast Error Feedback n Integration and Gain Control

Electronics Overview (cont’d) n Analog Devices ADu. C-70 xx series Micro -Controller n n

Electronics Overview (cont’d) n Stanford Research SIM 900 Crate n n n Off the

Current Status n n n PCB and enclosure in hand assembled Bench Testing completed

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

Design Goals n Lock-In on Cavity Resonance n n Slow and Fast Laser Frequency Scan Slow and Fast Error Compensation Incorporate on board micro-controller Compatible with Stanford Research SIM 900 Crate

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

Electronics Overview n Slow and Fast Laser Frequency Scan n Search for Signal of Interest n n n External Modulation n n Slow Scan Rate – 0. 01 Hz – 1 Hz Fast Scan Rate – 3 Hz – 30 Hz 10 -30 m. V @ 1 MHz Signal Error Input and Output n Polarity Selection (+/-)

Electronics Overview (cont’d) n Slow and Fast Error Feedback n Integration and Gain Control Loops (PI) n n n Gain Range – x 0. 1 – x 1 Integration Time – 1 m. S – 10 m. S Optional Features n n Trigger Monitor or Input Threshold Monitor or Input

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

Electronics Overview (cont’d) n Stanford Research SIM 900 Crate n n n Off the shelf “Modular System” GPIB and RS-232 interface Regulated Power Supply

More Electronics Overview

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