The 1.6 μm laser is located in the safe band of the human eye and has a high transmittance in the atmosphere. And 1.6μm is located in one of the atmospheric laser transmission windows, the transmission distance is farther, the corresponding distance and resolution and speed resolution are more accurate, and the corresponding photodetector parts have high detection sensitivity. Because of these characteristics, the 1.6μm laser is suitable for optical communication.
Theotry
The main components of device are:
Gain medium - Er：YAG
The 4I11/2~4I13/2 and 4I13/2~4I15/2 transitions of the Er3+ ion produce laser radiation in two mid-infrared bands. The wavelength of the 4I11/2~4I13/2 transition is 2.7 μm~3 μm. 4I13/2~4I15/2 can emit at a wavelength of around 1.6 μm, which can meet the needs of space optical communication and other fields.
Electro-optical Q-switching is to realize Q-modulation by using the electro-optic effect of the crystal, inserting a polarizer in the cavity, and using a polarizing plate to polarize and detect the wavelight. The use of BBO crystals as electro-optic crystals has following advantages: no birefringence effect, high damage threshold, and low insertion loss. Pressurized electro-optic Q-switching requires the insertion of a quarter-wave plate（QWP）between the electro-optic crystal BBO and the polarizer.
E-O Q-switch：BBO
Mirror——M1 – input mirror. High-transmittance for 808nm pump light, and high-reflection for 1.6μm. M2 – output mirror. High-reflection for 808nm, and it is transmittance for 1.6μm is 13%.
Compared with other band lasers, lasers with a working wavelength of 1.6μm are located in the human eye safety band and are also in the atmospheric transmission window. They have wide application and good development prospects in the fields of laser radar and space free communication.
Feature
- At atmospheric transmission window
- In the human eye safety band
- Long transmission distance
- Good beam quality
Application
- Coherent Doppler Radar Source
With the continuous deterioration of the global environmental climate, the data demand for atmospheric wind field is becoming more and more urgent. The coherent Doppler laser wind radar has high measurement accuracy and large measurable range, and has gradually become the main tool of atmospheric wind field. The Er:YAG crystal produces a 1.6μm band laser due to its 4I13/2~4I15/2 transition, which is just in the range of the opaque cornea of the human eye, and because its wavelength range is located in the atmospheric transmission window, the transmission loss in the atmosphere is small, so it acts as a laser radar source have certain research significance.
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