All-solid CW Intra-cavity Frequency-Doubled And Frequency-Stabilized Nd: YVO₄/LBO Red Laser

As well-known,laser-diode-pumped solid-state lasers(DPSL) have high efficiency,nice beam quality,compact configuration,and long lifetime, laser-diode-pumped continuous wave red lasers have been extensively applied in military affairs,medical treatments,scientific researches and so on. Especially,the single-frequency DPSL are required in a lot of applications such as spectroscopy,coherent measurement and holography.Since the wavelength of 1.3μm is the transmission window of silicon fiber,the lasers at 1.3μm have important application for the optical communication in fibers. All-solid-state red lasers have shown broad potential applications in color displays,biomedical,and pumping sources for tunable Cr:LiSAF lasers. The entangled light at 1342nm can be obtained via the process of frequency down-conversion in an optical parametric oscillator(OPO),where the single frequency red laser at 671nm has to be used as the pump source.The entangled optical beams at 1342nm will be an effective quantum system for developing long-distance quantum communication in optical fibers.The presented laser resonator is in a ring configuration consisting of four mirrors and a YVO₄-Nd:YVO₄ composite crystal end-pumped by a laser-diode serves as the laser material.A type-I critical phase-matched LBO crystal is placed inside the resonator to be used for the intra-cavity frequency-doubler.A TGG crystal and aλ/2 wave-plate are used for forcing the laser to operate unidirectionally.Under the pumped power of 19W,the single-frequency second-harmonic-wave output of 610mW at 671nm wavelength and the fundamental laser output of 400mW at 1342nm are obtained,simultaneously.The intensity fluctuation of the output red laser was less than±0.6%in 30 minutes.The laser frequency shifts at 1342nm wavelength were better than±1MHz and +5MHz within 1 minute, respectively.The thesis consists of the following four chapters:Chapter 1:Introduction The development history and physical features of DPSL are briefly reviewed and the research achievements of red solid-state lasers up-to-date are summarized.Chapter 2:Theoretical analysis of LD end-pumped solid-state laserBased on the rate-equation theory of four-level system,the expressions of threshold pump power,output power and slope efficiency are given.The thermal effect of laser crystal is investigated,the operation principle of intra-cavity frequency-doubler is analyzed,and the relationship between the efficiency of frequency-doubling and the phase match is considered.Above discussions provide the necessary theoretical basis for designing high power all-solid-state single frequency red laser.Chapter 3:Design and realization of the laser systemThe concept,character and advantage of the YVO₄-Nd:YVO₄ composite crystal are described.The experimental and theoretical study about the influence of the different doped concentration of laser crystal to the output power of the second harmonic wave at 671nm is presented.The three dimensional temperature distributions and the side view graphs after the thermal deformation of the conventional crystal and the composite crystal are compared.The character of LBO crystal is described.The dependence of the output power at 671nm on the lengths and phase match of doubling crystals is experimentally analyzed.The functions of the stability parameter((A+D)/2) and the waist spot of the vibrating laser beam versus the distance between two concave mirror are given,respectively.Utilizing the home-made laser, the single-frequency second harmonic wave output of 610mW at 671nm wavelength and the fundamental laser of 400mW at 1342nm are obtained, simultaneously.Chapter 4:Conclusion and outlook...