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The motive of doing this is to attend enough information, to use AOM as power modulator for the tweezer. AOM (Gooch & Housego R23080-2-1.06-LTD; 138252) operates in CW and normal mode. We use 1st order diffracted beam. First CW mode operation is characterized, to know the usable power (of the diffracted beam) Vs ascending input laser power. Second normal mode operation is characterized: Computer controlled ascending input voltage for RF signal power Vs usable power of the diffracted beam, at several input laser powers. The laser temperature is kept constant at 62F.
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 1st order beam power. This 1st order beam power is the usable power for tweezer. The data is presented below:
The relationship is linear. So the AOM gives output power in 1st order diffracted beam, of average around 70% of the input power (in CW mode). This help us calculating the usable power of any input power without measuring; for example if I set the laser on .10W, then the usable power at the tweezer is 70% of it, which is .07W or 70mW.The maximum usable power for the tweezer 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).
Normal mode operation characterization
In normal mode, AOM is controlled by our LabView program. Voltage input for RF signal is from –ve1 Volt to –ve5 Volts in –ve.1 Volt increment. 1st order diffracted beam power is recorded for every ascending voltage increment for .5W, 1.5W, 2W and 2.5W input laser powers. Different laser powers are used to check if any how the characteristic of the AOM is input power dependent, which it should not be. RF signal Vs diffracted beam power will help us in obtaining the best workable range of voltages over which power increases linearly. I will also help us in characterizing the relationship between the voltage and diffracted power. The data is presented below: