Investigation On Residual Amplitude Modulation In The Side-band Frequency Locking Scheme To Generate The 795 Nm Squeezed Light

With the development of quantum theory and technology,our ability to understand and control the microscopic quantum world has continued to increase.Quantum states will play an important role on improvement of society.Especially,the optical squeezed state,a non-classical state,is a kind of quantum correlation in essence.And it can be applied in quantum precision measurements such as gravitational wave detection,weak magnetic field measurement.There are lots of methods to Generate the squeezed light,one of which is optical parametric oscillation.we generated the CV vacuum squeezed light resonant with the Rb 1 line in a experimental scheme which have many PDH phase modulation feedback control loops to lock the cavity length and relative phase of lights.However,The residual amplitude modulation RAM in the PDH phase modulation shifts the zero baseline of the lock point of the optical resonator,more over,the RAM randomly fluctuates with the ambient temperature,resulting in detuning of the cavity length,which is equivalent to introducing the phase noise of the optical field and the phase noise will break the level of squeezing.Therefore,the purpose of this paper is to suppress the residual amplitude modulation(RAM)in the phase modulation.This Paper mainly includes the following sections:1.The important application background and research progress of vacuum squeezed light and the suppression of RAM at home and abroad is introduced.The fundamental theory of nonlinear optics including SHG and the generation in optical parametric oscillation cavity and detection of squeezed light is outlined.2.The principle of the PDH phase modulation used for locking cavity and the physical basis of the electro-optical effect are introduced.The half-wave voltage of the manufactured crystal is calculated.The half-wave voltage of the single-wedge crystal EOM is 187 V and that of the double-Brewster angle EOM is 486 V,but the modulator is Resonant type,the actual half-wave voltage is greatly reduced;using an impedance analyzer to measure the impedance characteristics of the electro-optic modulator,an LC resonant circuit and an L-type impedance matching network are fabricated.At an 8 MHz modulation frequency,the reflection coefficient of the 4°-angle crystal EOM is At 3%,the double-Brewster angle EOM,less than 1%.3.Compared with the rectangle crystal commercial EOM,the RAM noise power spectrum peak at the 8MHz modulation frequency of single-wedged crystal EOM is suppressed by 30 d B,and that of the double-Brewster angle EOM is suppressed by 25 d B.And the zero point shift of error signal of the home-made EOM at one hour is less than that of the commercial EOM by 24 times.Using a single-wedged crystal modulator and Newfocus modulator to lock the optical resonator cavity and relative phase,the effect of RAM on the level of squeezing was investigated.The experimental results show that the self-made crystal EOM is better.4.The appendix section describes the research of an external cavity feedback semiconductor laser IF-ECDL with 852 nm narrowband filter.The laser wavelength tuning range is 14 nm.The linewidth of a single filter is about 211 k Hz and that of The ECDL with double filters is187 k Hz.The laser frequency tuning range is Greater than 1.5GHz by scanning piezoelectric ceramic actuted on feedback mirror.