Laser Stabilisation for two-photon Rydberg transitions

Introduction

Rubidium atoms are excited to Rydberg states using a two-photon transition from the 5S_1/2 ground state. First the atom is excited from to the 5P_3/2 excited state using a 780nm DL100 laser, followed by a second transition at 480nm from 5P_3/2 to nS or nD Rydberg states using a high power frequency doubled TA\DL-SHG 110 system.

To stabilise the lasers to the two-photon transition, the 780nm probe laser is locked to a modulation transfer signal generated using an EOM with a 10MHz modulation frequency. Having locked the probe beam, the 480nm laser is then locked using the EIT signal from a thermal cell.

Laser systems

Currently there are two systemsFor the experiments performed using these laser systems a key parameter is the relative linewidth of the two-photon transition. In order to reduce this, the lasers are locked using a Fast Analog Linewidth Control (FALC) module which uses very fast current feedback to make corrections to the linewidth with a bandwidth ~10 MHz alongside a slow piezo feedback to give larger frequency correction.

 in operation, which are described below:

Lab 54:

• DL100-PRO 780nm Probe laser
• TA\DL-SHG 110 with DL-MOD laser head
• Both lasers use prototype FALC modules

Lab 56:

• DL100-MOD 780nm probe laser
• TA\DL-SHG 110 with DL-PRO laser head
• Both lasers use new FALC modules

General Information:

DL100 grating stabilized diode laser An overview of the DL100 laser head

DL-PRO vs DL-MOD Explanation of the difference between DL-MOD and DL-PRO current modulation

TA\DL-SHG 110 An overview of the frequency doubled laser system

FALC Description of how the FALC works

Optimisation and Trouble Shooting:

Setting up a FALC lock

480nm laser System Optimization

Trouble Shooting

Piezo Lifetimes

System Specific Information:

Lab 54 TA\DL-SHG Power Record

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