All-solid-state miniature laser gyroscope based on a single monolithic non-planar ring oscillator

He-Ne gaseous ring-laser gyroscopes (RLGs) have brought great breakthroughs in numbers of fields such as inertial navigation and attitude control in the past 50 years. However, their counterparts of all-solid-state, active RLGs have been far behind even though they have a few indispensable advantages. Here, we propose and demonstrate an all-solid-state, active RLG based on a millimeter-sized, single monolithic non-planar ring oscillator (NPRO) with a gain medium of Nd:YAG crystal or Nd-glass. The clockwise (CW) and counter-clockwise (CCW) laser modes in NPRO are simultaneously initiated under a regime of laser feedback interferometry, whose nonzero frequency difference intrinsically formats the single monolithic NPRO working as a Sagnac laser gyroscope without a noticeable lock-in effect. The higher wavefront distortion in NPRO samples is revealed to introduce less mode competition (higher beat frequency stability) between the two laser modes, which is a precondition to build the NPRO gyroscope. Under a free-running condition, the NPRO gyroscope typically has a bias instability of 31.3 deg /h and an angle random walk of 0.22 deg /h with a scale factor of 38.3 Hz /( deg s −1 ), and the instability is mainly caused by the magnetic noise at present. The NPRO gyroscope can be enclosed in a centimeter-sized package, with a power consumption below 0.7 W and a mass under 20 g. Moreover, the stability performance can be further improved by NPRO design and active noise suppression in the future. Such compact, low-power-consumed, and highly stable RLGs may find important applications in aerospace, defense, and industry.