# User:Pranav Rathi/Notebook/OT/2010/05/12/Characterization of AOM module

(Difference between revisions)
 Revision as of 13:51, 15 November 2012 (view source) (→Result:)← Previous diff Revision as of 13:54, 15 November 2012 (view source) (→Result:)Next diff → Line 15: Line 15: '''''The relationship is linear. AOM gives an average output power of 70% in 1st order diffraction beam .''''' This help us calculating the usable power of any input power without measurement; for example if I set the laser on .10W, then the usable power at the tweezers is 70% of it, which is .07W or 70mW. The maximum usable power for the tweezers is 2.66W. If we want to stay in the single mode operation regime, it is 1.4W (at room temperature). When the laser is cooled down to 60F, it is stretched to 1.9W (2.75W input). '''''The relationship is linear. AOM gives an average output power of 70% in 1st order diffraction beam .''''' This help us calculating the usable power of any input power without measurement; for example if I set the laser on .10W, then the usable power at the tweezers is 70% of it, which is .07W or 70mW. The maximum usable power for the tweezers is 2.66W. If we want to stay in the single mode operation regime, it is 1.4W (at room temperature). When the laser is cooled down to 60F, it is stretched to 1.9W (2.75W input). - ''Note: This study was done with 10634nm 4W coherent compass laser. My study showed that this particular laser trips to higher transverse modes at the power above 1.7W [[User:Pranav_Rathi/Notebook/OT/2010/04/13/Mode_profiling_at_high_power]]. + ''Note: This study was done with 10634nm 4W coherent compass laser. My study showed that this particular laser trips to higher transverse modes at the power above 1.7W. - Later on we replaced this laser with 1064nm 2W crysta laser which did not have any of the problems [[User:Pranav_Rathi/Notebook/OT/2010/08/18/CrystaLaser_specifications]].'' + + [[User:Pranav_Rathi/Notebook/OT/2010/04/13/Mode_profiling_at_high_power]] + + Later on we replaced this laser with 1064nm 2W crysta laser which did not have any of the problems. + + [[User:Pranav_Rathi/Notebook/OT/2010/08/18/CrystaLaser_specifications]]'' ===Normal mode operation characterization=== ===Normal mode operation characterization===

## AOM Characterization

### Introduction:

I am going to use AOM as power modulator for the tweezers: AOM (Gooch & Housego R23080-2-1.06-LTD; 138252) operates in CW and normal mode.I am using 1st order diffraction beam. So there is need to characterize 1st order in CW and normal mode. In cw mode-operation characterization is done; power output in 1st order diffraction beam Vs input laser power in ascending order. In normal mode-operation Characterization is done; analog RF-input voltage Vs output power in 1st order diffraction beam, for several input laser powers. I control laser power in 1st order diffraction beam through NI-DAQ (which applies an analog voltage signal from 1 to 5 volts in any increments) controlled by "feedback control 96main" program written in Labview V7.1.

### Setup:

Relatively simple setup ThorLabs power meter is place infront of the diffracted beam from AOM. An aperture is used infront of the power meter to keep off all the stray beams.

### CW mode operation characterization:

The AOM is operating in CW mode. Data is recorded; laser power (.25W to 4W in .25W increments) Vs lase power in 1st order diffraction beam. The laser power in 1st order diffraction beam is the usable power for optical tweezers. The data is presented below:

#### Result:

The relationship is linear. AOM gives an average output power of 70% in 1st order diffraction beam . This help us calculating the usable power of any input power without measurement; for example if I set the laser on .10W, then the usable power at the tweezers is 70% of it, which is .07W or 70mW. The maximum usable power for the tweezers is 2.66W. If we want to stay in the single mode operation regime, it is 1.4W (at room temperature). When the laser is cooled down to 60F, it is stretched to 1.9W (2.75W input).

Note: This study was done with 10634nm 4W coherent compass laser. My study showed that this particular laser trips to higher transverse modes at the power above 1.7W.

Later on we replaced this laser with 1064nm 2W crysta laser which did not have any of the problems.

### Normal mode operation characterization

In normal mode, AOM is controlled through NI-DAQ by LabView program. Voltage input for RF signal is from 1 Volt to 5 Volts in any Volt increment. 1st order diffracted beam power is recorded for every ascending voltage increment of .1Volt for .5W, 1.5W, 2W and 2.5W input laser powers. Different laser powers are used to check: If the characteristic of AOM is input power dependent, which it should not be. RF-input voltage Vs 1st order diffracted beam power will help us in obtaining the best workable range of voltages over which power increases linearly. It will also help us in characterizing the relationship between the voltage and diffracted power. This is very important in data analysis. While data acquisition we can not measure the laser power in trap its is unpractical but if know the characteristic RF-input voltage Vs laser power in trap we can calculate the laser power in trap from the voltage. The data is presented below: