Dichroic Atomic Laser Locking Setup. Kevin W. Vogel University of Michigan Physics Raithel Research Group. 3 August 2004

Size: px

Start display at page:

Download "Dichroic Atomic Laser Locking Setup. Kevin W. Vogel University of Michigan Physics Raithel Research Group. 3 August 2004"

Mae Dickerson
5 years ago
Views:

1 Dichroic Atomic Laser Locking Setup Kevin W. Vogel University of Michigan Physics Raithel Research Group 3 August 2004 Contents Overview 2 Materials.3 Rubidium Cell and Magnets Setup.4 Locking Signal Circuit 5 Temperature Control System..7 1

2 Overview This document provides detail on the Dichroic Atomic Laser Locking (DAVLL) setup installed on the Advanced Physics Lab 4268 magneto-optical trap. This method uses a magnetic field to split the Doppler-broadened absorption signal into its Zeeman components. The output of the ECDL is linearly polarized. Linearly polarized light can also be thought of as equal amounts of right and left circular polarized light. When the light passes though the rubidium vapor cell in a uniform 100-G magnetic field, the different circular polarizations are absorbed by one of the Zeeman transitions. The Zeeman transition m F = 1 is of greater frequency than the original transition frequency and absorbs the right-circular polarized light. The Zeeman transition m F = -1 is of lesser frequency than the original transition frequency and absorbs the left-circular polarized light. The light then passes though a circular polarization analyzer, which consists of a quarterwave plate and a linear polarizing beam splitter. The analyzer separates the right and left circular polarized components of the laser light and the signals are received by photodiodes. Each photodiode signal produces a Doppler-broadened transition spectrum, one shifted to a greater frequency and the other to a lesser frequency, with a peak to peak difference of ~ 500 MHz. The difference between the two signals gives an antisymmetric error signal that contains the locking slope. To increase signal stability several items were added. A 100mm focal length lens was used to ensure all light was received by the photodiodes. A circuit box was made containing the polarizing beam splitter and the necessary electrical components to produce the locking signal, thus reducing circuit noise. Since permanent magnets are highly temperature dependent, the rubidium cell and magnets were placed in a temperature-controlled box. 2

3 Materials Complete Materials List 1 ConOptics box 1 Glass slide 1 Rubidium cell 16 Ceramic permanent magnets 1 2-1/4 diameter x 3-1/2 length PVC pipe holder 1 1-7/8 diameter x 1/4 length PVC pipe spacer 1 Aluminum stand 1 Quarter wave plate w/ stand 1 100mm focal length lens w/ stand 1 2-3/4 x 4 x 2 electronics box w/ screws and stand 1 2-1/2 x 2-1/4 aluminum plate 1 1cm polarizing beam splitter 2 Photodiodes 3 1k resistors 1 10k resistor 1 OP27 low noise, precision operational amplifier 1 switch 3 BNC female connectors 1 2 x 3 circuit board 4 nylon nuts (used as spacers beneath circuit board) 1 rubber heater 1 temperature control circuit Purchased Materials Master Magnetics, Inc. The Magnet Source Ceramic ring magnets Part #: CR162 Price: $0.60 each ($30 minimum order) Quantity: 16 Minco Products, Inc. Standard rubber heater, 8.5 ohms, 19 in. x 1 in. Part #: R5348R8.5L12BU Price: $27.50 Quantity: 1 3

Rubidium Cell and Magnets Setup Above is the magnet setup containing the rubidium vapor cell. Eight ceramic magnets are on either side of a center spacer.

4 Rubidium Cell and Magnets Setup Above is the magnet setup containing the rubidium vapor cell. Eight ceramic magnets are on either side of a center spacer. The spacer is notched for the glass nub of the cell. For support, this was enclosed in a PVC pipe. To keep the round apparatus from moving, a simple aluminum stand was made. Diagrams of the stand and spacer are below. Material for spacer, PVC pipe, and stand were taken from shop scraps. Making the aluminum stand longer would eliminate the need for the PVC pipe. 4

The beam splitter is attached to the board with double-sided tape.

5 Locking Signal Circuit Above is the circuit box that produces the locking signal. The circuit diagram and setup have been provided below. Note the polarizing beam splitter is contained inside the box. The beam splitter is attached to the board with double-sided tape. The board is isolated from the metal box with four nylon nuts used as spacers and attached using double-sided tape. The photodiodes should be equidistant from the beam splitter so the lens focuses on both. OP27 Diagram 5

6 Here is a rough sketch of the electronics box. 6

7 Temperature Control System The temperature control system has not yet been completed. Holes were drilled in each end of the wooden box. Half of a microscope slide was glued over each hole to prevent airflow. NASA SHARP student Alex is currently making the temperature control circuit. See him for further details regarding this circuit. An alternative to making your own heating circuit is to purchase one. Here is the order information of one that was used in the past by Tara. Wavelength Electronics amp temperature controller Part #: HTC-3000 Price: $109 Quantity: 1 7

Roger Ding. Dr. Daniel S. Elliott John Lorenz July 29, 2010

Roger Ding. Dr. Daniel S. Elliott John Lorenz July 29, 2010 Roger Ding Dr. Daniel S. Elliott John Lorenz July 29, 2010 Overall Project Goal: Photoassociation of Li and My REU Goals: Work on electronics to help control the dualspecies magneto-optical trap (MOT)