YuefanGuo - 19:21, Wednesday 07 December 2016 (343)
Green light
Member: Matteo, Eleonora,Yuefan
We did the clean-up of the SHG housing today, installed the crystal, mounted the harmonic beam splitter and SHG housing, and finally we got the green light. But during the process of finding the green light, we installed another half-wave plate between the second and third lens of telescope, because of the design of the SHG housing, the polarization is not we thought it should be. In the attachment you can find the situation of the optical bench now. The installation of other two harmonic beam splitter is for the power measurement of the pure green light instead of the mixture of the green and infrared.
We did three groups of measurement:
1.The relationship between the resistance(temperature) and the green light power. Since the thermal controller we are using now cannot show directly the temperature of the SHG, it can only shows the resistance. During this measurement, the diode current of the laser is 1.996A and the temperature of laser crystal is 23.63 degree. From the figure, you can find out that when the resistance is about 3.375, the power reach its peak. According to the manual of the thermal sensor, 3.011 kilo ohm response to 60 degree and 4.147 response to 50 degree. So the phasing matching temperature of the crystal is lower than what we thought it should be at 65 degree.
2.The relationship between the laser crystal temperature and the green light power. Under the circumstance with resistance setting to 3.375 kilo ohm. Since this kind of laser can have two modes in the same time at some temperature which will increase the power of green light to 1.5 times, these temperature points are where we should avoid. The red circle with plus marker in the figure is the temperature we used before. It is in the middle of two unexpected point, so we can still set the temperature there.
3.The last one is to show the linear relationship between the power of infrared and green, since they both linear dependent with diode current of the laser.
We did the clean-up of the SHG housing today, installed the crystal, mounted the harmonic beam splitter and SHG housing, and finally we got the green light. But during the process of finding the green light, we installed another half-wave plate between the second and third lens of telescope, because of the design of the SHG housing, the polarization is not we thought it should be. In the attachment you can find the situation of the optical bench now. The installation of other two harmonic beam splitter is for the power measurement of the pure green light instead of the mixture of the green and infrared.
We did three groups of measurement:
1.The relationship between the resistance(temperature) and the green light power. Since the thermal controller we are using now cannot show directly the temperature of the SHG, it can only shows the resistance. During this measurement, the diode current of the laser is 1.996A and the temperature of laser crystal is 23.63 degree. From the figure, you can find out that when the resistance is about 3.375, the power reach its peak. According to the manual of the thermal sensor, 3.011 kilo ohm response to 60 degree and 4.147 response to 50 degree. So the phasing matching temperature of the crystal is lower than what we thought it should be at 65 degree.
2.The relationship between the laser crystal temperature and the green light power. Under the circumstance with resistance setting to 3.375 kilo ohm. Since this kind of laser can have two modes in the same time at some temperature which will increase the power of green light to 1.5 times, these temperature points are where we should avoid. The red circle with plus marker in the figure is the temperature we used before. It is in the middle of two unexpected point, so we can still set the temperature there.
3.The last one is to show the linear relationship between the power of infrared and green, since they both linear dependent with diode current of the laser.
Images attached to this report
