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Researches On The Technique Of All Solidified Laser For LIDAR

Posted on:2014-08-04Degree:DoctorType:Dissertation
Country:ChinaCandidate:L Q NiuFull Text:PDF
GTID:1268330422459345Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
Laser is the core of LIDAR, which has a great impact on the key parameters ofLIDAR system. And3D imaging LIDAR based on the pulse ranging mechanismplays an important role in the system of LIDAR, which is an active device in that itcarries its own transmitter and does not depend on ambient radiation. As thetransmitter of3D imaging LIDAR, Laser must be required to some specialcharacteristics, such as high repetition rate, narrow temporal duration, excellentbeam quality, high efficiency, robust, and so on. This dissertation focuses on twokind laser technologies for the applications of3D imaging LIDAR: a passivelyQ-switched microchip laser and Yb3+-doped pulse all-fiber amplifier based onMOPA structure. Meanwhile, the practical sample of pulsed all-fiber laser has beensuccessful developed and applied to the3D imaging LIDAR system.The main research works and innovations of this dissertation are summarizedas follows:1. Basing on the rate equations of Cr4+:YAG passively Q-switched laser,the output characteristics of pulsed laser as a function of twodimensionless variables are derived. According to the relationships, thelaser parameters including pulse energy, peak power, pulse width, andlaser efficiency are acquired by means of theoretical analysis andnumerical simulation. It is useful to define the laser parameters whenthe anticipant pulse energy.2. Single-and dual-pulse oscillation delivered from a LD pumpedpassively Q-switched Nd:YAG/Cr4+:YAG microchip laser has beeninvestigated under the different pump levels. And the dual-pulse waveform consists of a main pulse and a satellite pulse with respectiveintensities and optical spectra. Experimental results indicate that thedual-pulse emission results from double longitudinal mode oscillation.The preponderant oscillating mode gives birth to the main pulse, andthe other oscillating mode corresponds to the satellite pulse.3. A compact high power nanosecond all-fiber MOPA system based onYb3+-doped fiber amplifier system is established. Laser pulse withstable wavelength, controllable repetition rate and adjustable pulseduration is obtained. And the peak power is up to123kW. As thetransmitter of3D imaging LIDAR, it is benefit to improve thecapabilities of the entire system. Temporal duration and repetition rateof the laser pulse can choose flexible according to the different practicalapplication.4. The proposed fiber amplifier is used as the laser source ofthree-dimension (3D) imaging LIDAR system, which achieves thefunction of3D imaging and gives the scanning imaging results. Theperformance of the laser is verified. The imaging results show that theproposed fiber amplifiers with high peak power have the excellentreliability and stability and are very suitable for3D imaging LIDARsystem. The3D scanning image has the ranging resolution of1.86cm,the ranging accuracy of±7.5cm, and the angular resolution of0.009°.
Keywords/Search Tags:all solidified laser, LD pumping, saturable absorber, microchip laser, passive Q-switching, cladding pumping, fiber amplifier, MOPA
PDF Full Text Request
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