Fig. 1. Schematic of the frequency stabilization scheme based on a semi-external-cavity HeNe laser. BS, beam splitter; PD, photodiode; NTC Plane, negative temperature coefficient plane; DAQM, data acquisition module; TCM, temperature control module.

Fig. 2. Schematic of holes burnt on the gain curve in the cases of (a) one resonant longitudinal mode and (b) three resonant longitudinal modes.

Fig. 3. Schematic diagram of holes burnt on the gain curve in the case of equal proportion of dual neon isotope medium.

Fig. 4. Simulation results of the hole depths d₁₍₁₎ and d₃₍₁₎ of the two side modes as a function of frequency difference Δυ with different variable parameters in terms of (a) the loss of resonant cavity L_r; (b) the capillary length l; (c) the capillary diameter ϕ; (d) the length of resonant cavity L; (e) the homogeneous linewidth Δυ_L; and (f) the abundance ratio of Ne isotopes R.

Fig. 5. Theoretical intensity-tuning curve of a three-longitudinal-mode linearly polarized HeNe laser.

Fig. 6. Photograph of the experimental setup of the high-power and frequency-stabilized semi-external-cavity HeNe laser for short-exposure interferometry. PMI, polarization maintaining isolator; FPBC, fibre polarization beam combiner; VOA, variable optical attenuator.

Fig. 7. Output characteristics of the laser with temperature in terms of (a) the profile of the intensity tuning curve; (b) the range of the monomode operation interval; and (c) resonant mode distributions.

Fig. 8. Output characteristics of the semi-external-cavity HeNe laser in (a) mode search stage and (b) steady operation stage.

Fig. 9. Comparison of the contrast of the interferograms taken by our proposed laser and the commercial frequency-stabilized HeNe laser. Interferograms generated by (a), (b) the two lasers, where the interferometer is disturbed by a motor with 4000 rotations per minute, and (c) the commercial laser in the nonvibrating environment. The red solid curve in (d) represents the intensity on Line_1 of (a), while the blue solid curve in (d) shows the intensity on Line_2 of (b).