This study experimentally reveals the self-biasing phenomenon in prism laser gyros. When the gyro operates in a specific double longitudinal mode and four-frequency oscillation state, the gyro can detect the normal angular velocity component of the Earth’s rotation without dithering, the self-biasing status is induced. In this study, a laboratory platform of the self-biasing laser gyro is established. The two longitudinal modes oscillate on both sides of the gain curve. The intensity ratio of the strong and weak modes is about 1.4 to 1, and the coupling effects of these two modes with parallel linear polarization have been discussed using Lamb theory. Because the adverse effects of biasing technical are avoided, the self-biasing gyro has potential to challenge the strategic precision.

Frequency-difference-stabilized dual-frequency solid-state lasers with tunable and large frequency difference have become an ideal light source for the high-accuracy absolute-distance interferometric system due to their stable multistage synthetic wavelengths. In this work, the advances in research on oscillation principles and key technologies of the different kinds of dual-frequency solid-state lasers are reviewed, including birefringent dual-frequency solid-state lasers, biaxial and two-cavity dual-frequency solid-state lasers. The system composition, operating principle, and some main experimental results are briefly introduced. Several typical frequency-difference stabilizing systems for dual-frequency solid-state lasers are introduced and analyzed. The main development trends of research on dual-frequency solid-state lasers are predicted.

To stabilize the frequency-difference of the two-cavity dual-frequency Nd:YAG laser at 1064 nm, a quadrature-demodulated Pound–Drever–Hall (QD-PDH) frequency-difference stabilizing system has been designed, which is composed of two sets of QD-PDH frequency stabilizing subsystems sharing the same Fabry–Perot cavity as the frequency reference. Both phase modulators are driven by the signals with the same frequency of 10 MHz generated by a single direct digital synthesizer (DDS), and the DDS also outputs the other two orthogonal signals as the demodulation reference signals of both frequency stabilizing subsystems. A QD-PDH frequency-difference stabilizing system for a two-cavity dual-frequency Nd:YAG laser with a frequency-difference of ∼24 GHz at 1064 nm has been established and investigated experimentally. The experimental results have indicated that during a period of 1 h, the laser frequency stabilities of the linear and right-angle cavities are estimated by Allan variance to be better than 2.3 × 10 − 11 and 2.7 × 10 − 11, respectively, corresponding to frequency-difference stability of better than 4.2 × 10 − 7. Such a frequency-difference-stabilized two-cavity dual-frequency Nd:YAG laser can be used as an ideal light source for the synthetic-wave absolute-distance interferometric system.

In order to stabilize the self-biasing state of a laser gyroscope, a dual-longitudinal-mode asymmetric frequency stabilization technique was studied. The special frequency stabilization is based on the accurate control of the intensity tuning curve in the prism ring laser. In this study, the effects of the ratio of the Ne isotopes, the inflation pressure, and the frequencies coupling on the intensity tuning curve in a laser gyro were examined. The profiles of the intensity tuning curve were simulated under the mixing ratios of Ne²⁰ and Ne²² of 1:1 and 7:3, and the inflation pressures were 350 Pa, 400 Pa, and 450 Pa. The mixing ratio of Ne²⁰ and Ne²⁷ was dealt with similarly. The method for precisely adjusting the profiles of the intensity tuning curve was analyzed. The profiles were verified by experiments under different isotope ratios and pressures. Finally, based on a prism ring laser with an optical length of 0.47 m, the proposed frequency stabilization method was preliminarily verified.

To investigate the discharge parameters of the prism laser gyro under high-frequency excitation, a finite element simulation model is developed using a prism gyro structure with an optical length of 0.28 m. The optimal high-frequency excitation parameters were determined by simulating the effects of high-frequency discharge, voltage, size of the electrode plates, and horizontal displacement of the electrode plates on the gas discharge: high-frequency voltage is 6.5 to 7.5 V, frequency is 130±5 MHz, flat electrode discharge structure is used, and upper and lower electrode plates are 16×5×2 mm3 and 12×5×2 mm3, respectively. It is preferable that the center positions of both upper and lower plates be as symmetrical as possible. Finally, the experimental results validate the accuracy of the finite element analysis.

To stabilize the frequency difference of the two-cavity dual-frequency Nd:YAG laser at 1064 nm, a scheme of the phase modulation of the orthogonally and linearly polarized dual-frequency laser using single electro-optic phase modulator has been proposed, and a frequency-difference stabilizing system for a two-cavity dual-frequency Nd:YAG laser based on the single-modulator quadrature-demodulated Pound–Drever–Hall (SM-QD-PDH) method has been designed and established. The characteristics of phase modulation, frequency discrimination, frequency stabilization, and frequency-difference stabilization of the orthogonally and linearly polarized dual-frequency laser with a frequency difference of ∼24 GHz at 1064 nm have been investigated experimentally. The experimental results have indicated that during a period of 1 h, the laser frequency stabilities of the linear and right-angle cavities are estimated by Allan variance to be better than 1.6 × 10 − 11 and 2.0 × 10 − 11, respectively, corresponding to a frequency-difference stability of better than 2.9 × 10 − 7. The designed SM-QD-PDH frequency-difference stabilizing system is not only simple but also has better performances than that of the double-modulator QD-PDH frequency-difference stabilizing system. Such a frequency-difference-stabilized two-cavity dual-frequency Nd:YAG laser can be used as an ideal light source for the synthetic-wave absolute-distance interferometric system.