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J. Eur. Opt. Society-Rapid Publ. 22, 55( 2026)
Figure 8. The power stability of the signal light and the idler light, and the output spot of the signal light.
Figure 9. The output powers of the signal and idler lights at different wavelengths under 5.0 W pump power.
Table 1. Comparison of key performance parameters between the present shared-cavity OPO and previous works.
Structure |
Oscillation threshold |
Wavelengths |
Output power Efficiency System dimensions Reference |
Intra-cavity |
2.8 W |
3.2 lm |
410 mW |
7.7 % |
> 140 mm |
[ 7 ] |
Intra-cavity |
1.6 W |
3.52 lm |
65 mW |
2.2 % |
/ |
[ 20 ] |
Self-intra-cavity |
> 8 W |
3.86 lm |
0.38 W |
2.5 % |
> 128 mm |
[ 9 ] |
Intra-cavity |
2 W |
3.3 lm |
1.32 W |
7.2 % |
> 200 mm |
[ 21 ] |
Extra-cavity |
1.86 W |
3217 nm |
1101.2 mW |
12.5 % |
> 300 mm |
[ 12 ] |
Shared-cavity |
6.9 W |
1476.4 nm, no idler |
580 mW |
/ |
120 mm |
[ 13 ] |
Shared-cavity |
0.9 W |
3833.2 nm |
187 mW |
3.7 % |
70 mm |
Here |
Meanwhile, the output power stability of the signal light and the idler light is measured over a period of two hours, as shown in Figure 8, with power fluctuations of 2.6 % and 1.5 %, respectively. The stability of the signal light is slightly poorer, which is primarily caused by the parasitic oscillations in the visible light. The output beam spot of the signal light at 1472.9 nm is also shown in Figure 8, which is measured using a slit-scan beam profiler( Beam ' R2, DataRay Inc.). The output spot has good symmetry and an ellipticity of 0.98, along with a Gaussian energy profile. The M 2 factor is measured to be approximately 1.3. These results confirm the favorable performance of the shared-cavity structure, reflecting its high quality and proper alignment.
When the PPMgLN’ s periods are 28.6, 28.8, 29.0, 29.2 and 29.4 lm respectively, the idler powers of the mid-infrared wavelengths at 4114.8, 4046.9, 3977.2, 3907.0 and 3833.2 nm are 136, 149, 158, 167 and 187 mW under the 5.0 W pump power, respectively, as shown in Figure 9.
3.4 Performance comparison
To directly evaluate the performance of our shared-cavity OPO against state-of-the-art configurations, we summarize in Table 1 the key parameters of the present system together with those of representative previous works [ 7, 9,
12
, 13, 20, 21 ]. As summarized in Table 1, the shared-cavity OPO presented in this work exhibits several distinct advantages over previously reported configurations. First, the oscillation threshold of 0.9 W is the lowest among all compared systems. Second, the total length of 70 mm is the most compact, which is enabled by eliminating separate pump coupling optics. Third, despite the simplicity of the design, the mid-IR output performance( 187 mW at 3833.2 nm, 3.7 % efficiency) is competitive with or better than many more complex systems. Our efficiency is competitive with those of reported intra-cavity and extra-cavity OPOs. The main limiting factors are round-trip + loss 4 %( including 2 % output coupling and 2 % other losses), mode overlap integral 0.96, and parasitic nonlinear processes.
It is also important to note that both intra-cavity and extra-cavity configurations typically require multiple cavity mirrors and / or external coupling lenses, leading to larger footprints and more critical alignment procedures. In contrast, our shared-cavity architecture uses only two mirrors( M in directly coated on the Nd: YVO 4 crystal and M oc as the output coupler) and no additional beam-shaped optics. This inherent simplicity not only reduces the system size but also improves long-term stability and ease of operation.