Abstract
This work is to demonstrate the feasibility of a cavity-enhanced parity non-conservation (PNC) induced optical rotation experiment. It proposes that, with a non-orthogonal atomic beam system, the reciprocal circular birefringence of PNC induced optical rotation can be cleverly converted to non-reciprocal circular birefringence and hence provide a continued increase of optical rotation in a linear cavity. Such an enhancement cavity configuration can be an ultrasensitive polarimeter based on noise-immune cavity enhanced optical heterodyne molecular spectrometer (NICE-OHMS) technique. In this thesis, a 1.28 um NICE-OHMS apparatus has been constructed for the future PNC experiment. The wavelength region of 1.28 um is particularly important for several magnetic dipole transitions of various atomic systems for PNC optical rotation measurements, such as lead, thallium, ytterbium and iodine. To access the wavelength of the 1.1-1.3 um region, the spectroscopic characteristics of a quantum-dot (QD) laser with the external cavity configuration were investigated. The residual electroluminescence, due to the inhomogeneous broadening of QD gain medium, was observed and filtered out using a grating. While a fiber-coupled electro-optical modulator (EOM) was employed, a wide-bandwidth (~800 kHz) locking of a QD-ECDL to a high-finesse (F=18500) cavity had been demonstrated using the Pound-Drever-Hall technique. The laser linewidth of the QD-ECDL has been narrowed to 1 kHz level (1 ms), then the laser was applied to NICE-OHMS for observing weak transitions. The spectrum of weak nitrous oxide transitions at 1.283 um are obtained with a signal-to-noise ratio of 30 for gas pressure of 54~mTorr. For system diagnosis, the minimum noise-equivalent absorption coefficient, alpha_{min}, 5.3*10^{-10} cm^{-1}Hz^{-1}, had been reached. That infers the minimum fractional absorption to be 6*10^{-9} at 1 s integration time, comparable to the other Doppler-broadened NICE-OHMS experiments.