Theoretical And Experimental Study On All-solid-state Single-frequency Blue Ti:sapphire Laser Around 461 Nm

In the laser field,shorter-wavelength lasers——blue lasers(450 nm?480 nm)have wide applications in high-density storage,laser color display,underwater communications,laser medicine,laser imaging,spectroscopy and so on.Atomic clock is a device of frequency measurement standard which use the atomic or molecular level transition radiation frequency to lock an external oscillator frequency,that also known as quantum frequency standard or atomic frequency standard.In atomic clock experiments,there is a higher stability frequency to be need,and the speed of atoms is necessary to as smaller as possible.For the research of strontium atom clock,the dipole transition is on the basis of the(5s2)1 S0-(5s5p)1P1 state of the strontium atoms motivated by 461 nm.Thus,the blue laser at 461 nm is very important in the strontium clock system.In this paper,we demonstrate an all-solid-state intracavity frequency-doubled 461 nm blue Ti:sapphire laser with single-frequency operation,that provide a laser source for strontium atom clock research experiments.Its main contents are as follows:1.It analyzes the characters of gain medium-Ti:sapphire crystal.Then,combined with the equation of photon change rate,we get the threshold power equation on the bases of the quasi-four-level laser process of the radiation energy level in the Ti:sapphire.And find a theoretical method to reduce the laser threshold.Finally,we apply the results to our experiments and obtain the curve about the threshold pump power at 922 nm variations versus the beam waist at Ti:sapphire crystal.2.It introduces the birefringent phase matching and quasi-phase matching.Firstly,it analyzes the walk-off effect during the process of birefringent phase matching,and get the formula for calculating the best length of LBO crystal.Then it also introduces the method of quasi-phase matching without walk-off effect and design principle of periodically poled nonlinear crystal.3.A ring resonator consisting of six mirrors has been designed.In order to achieve single-frequency output and ensure the wavelength being tuned in a continuous range,we use an optical diode,three-plated birefringent filters and an etalon in the resonator.4.When we use the type-?phase matching LBO(3 mm×3 mm×7.3 mm)crystal as the intracavity frequency doubler,the highest power is 1.02W at the pump power of 14 W,the peak to peak fluctuation of the power is less than±1.3%,the optical-optical conversion efficiency from green laser to blue laser is 7.3%,and its beam quality values of M_x~2 and M_y~2 are 1.59 and 1.20,respectively.When we use the quasi-phase matching PPKTP(1 mm×2 mm×18 mm)crystal as the intracavity frequency doubler,the highest power is 1.05W at the pump power of 12 W,the peak to peak fluctuation of the power is less than±1.5%,the optical-optical conversion efficiency from green laser to blue laser is 8.75%,and its beam quality values of M_x~2 and M_y~2 are 1.05 and 1.04,respectively.