Lab_1. Basic Alignment of Laser and Optics
Introduction:
In this experiment, we learn to build an optical path to measure the spectrum of light.
The aim of this experiment is to measure the spectrum of white light, so we use white light LED as light source. We also need two other laser generators with known wavelengths to calibrate the axis of spectrum. Here we choose helium-neon laser which generates red light with a wavelength of 633 nm and semiconductor laser which generates green light with a wavelength of 532 nm.
A 小螺号歌曲helium–neon laser or He-Ne laser, is a type of gas laser whose gain medium consists of a mixture of 85% helium and 15% neon inside of a small electrical discharge. It usually works in the visible band, and the mostly used is red light with a wavelength of 633 nm. A semiconductor laser is a device that uses semiconductor materials to generate laser. We utilize it to generate green light with a wavelength of 532 nm.
To measure the spectrum, the most important element is the transmission grating, which determines the dispersion of polychromatic light and the formation of spectrum. Other elements are needed to confine the optical path and make sure the detector can receive the light signal.
A lens is used to focus a light beam by means of refraction. When the lens converges the light at a point, the signal received by the detector is closer to the ideal point, which can reduce the error. Optical attenuator can attenuate the light intensity. The attenuation of light is related to its type and thickness. Diaphragm is an entity in an optical system that limits the light beam. Its size can be adjusted by rotation. In the last step, we need to collect data with CCD sensors. CCD sensor can directly convert the optical signal into analog current signal. The current signal is amplified and analog-to-digital converted to achieve image acquisition, storage, and reproduction.
Methods and equipments:
1.该死的温柔mvAdjust parallel light with Semiconductor Laser.
1)Put semiconductor laser on the laser holder.
2)The optical elements are arranged on the optical platform, as shown in Fig. 1.
我在那一角落患过伤风Fig. 1 Optical path for measuring spectrum. A) The light path
we built. B) Schematic diagram of standard optical path
1)Turn on the semiconductor laser. Adjust the altitude and angle to get laser parallel to optical table.
2)Adjust the height of each optical element and use the white plate to verify whether the z
ero-order light can pass through the attenuator, diaphragm, transmission grating and the last diaphragm in turn. Use two diaphragm to ensure that the light emitted by the laser is collimated.
3)Place the lens to focus the first-order light, adjust the position of the lens, and make the green light pass through the lens from the center of the lens.
4)Use CCD to collect the light signal, adjust the position of the CCD back and forth, and determine whether the CCD is in the focal plane through the change in the size of the light spot in the computer software. At the same time, the green light signal is moved to the center of the image.
5)Save the data of green light.
6)Turn off the semiconductor laser.
2.Adjust parallel light with He-Ne Laser.
1)Turn on the He-Ne laser.
2)Only adjust altitude and angle of He-Ne laser to pass the same optical path determined before.
3)Save the data of red light.
4)Turn off the He-Ne laser.
3.Adjust parallel light with White Light LED
1)Turn on the White light LED.
2)Only adjust altitude and angle of White light LED to pass the same optical path determined before.
3)Save the data of white light.
4)Turn off the white light LED.
4.很靠近海Adjust parallel light with Mobile Flash
1)Turn on the mobile flash.
2)Only adjust altitude and angle of mobile flash to pass the same optical path determined before.
wonderfulgirl4)Turn off the mobile flash.
5.Data processing
The image we get is just the relationship between the number of pixels and the intensity, we need to convert the number of pixels to wavelength. To accomplish this conversion, we need to utilize the spectrum of the standard green light (532 nm) and red light (633 nm).
6.Equipment
He-Ne laser, Semiconductor laser, White light LED, Optical attenuator, Aperture, Transmi
ssion grating, Focusing lens.
Results and Discussion:
The light appears as a circle in the image [Fig.2], When we built the optical path, we did not ensure that the height of the components was consistent, resulting in the optical path itself being inclined. This may have no effect on the first calibrated laser, but with the second calibrated laser it is difficult to align, resulting in scattered calibration data collection for the standard red light. Therefore, I need to use a circle to fit the data and use the coordinates of the center of the circle as the coordinates of the light [Fig. 2]. The coordinates of the center of light I get are shown in Table 1.
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