Direct laser cooling is a very promising method to obtain cold molecules for various applications. However, a molecule with satisfactory electronic and optical properties for the optical scheme is difficult to identify. By suggesting criteria for the qualified molecules, we develop a method to identify the suitable polyatomic molecules for direct laser cooling. The new criteria from the equilibrium geometrical structures and fundamental frequencies of the ground and low-lying excited states are used to replace the past ones based on Franck–Condon factors. The new method can rapidly identify the preferable one among many candidate polyatomic molecules based on ab initio calculations because the new criteria are free from the construction of potential energy surfaces. The method is testified by using triatomic molecules containing OH. All the reported and two new molecules suitable for direct laser cooling are identified by comparing 168 electronic states of 28 molecules with the new criteria. The newly found molecules have been confirmed using the Franck–Condon factors from the construction of potential energy surfaces. Finally, the optical schemes for the direct laser cooling of the SOH and SeOH molecules are established.

High-performance optical isolators are key components in photonic integrated circuits, with significant applications in nonlinear optical systems. We propose a design for a TE-mode optical isolator based on the AlGaAs-on-insulator platform. The isolator consists of non-reciprocal phase shift (NRPS) waveguides, reciprocal phase shift (RPS) waveguides, and multi-mode interference (MMI) couplers achieving low loss, high isolation, and wide bandwidth. Numerical simulations show that, at a wavelength of 1550 nm, the device provides a bandwidth of 91 nm at 30 dB isolation. The confinement factors for a magneto-optical (MO) waveguide were analyzed, and a detailed loss analysis revealed a total loss of 1.47 dB and a figure of merit (FoM) of 2.76 rad/dB. The manufacturing tolerances of the isolator are discussed referring to the requirement of stability and reliability in practical applications. This study provides an optimized design for high-performance TE-mode optical isolators in integrated photonic systems, which are well-suited for efficient and stable nonlinear optical applications.

Integrated optical isolators are important building blocks for photonic integrated chips. Despite significant advances in isolators integrated on silicon-on-insulator (SOI) platforms, integrated isolators on GaAs-on-insulator platforms are rarely reported. In this paper, two structural designs of optical isolators based on the TM basic mode of GaAs-on-insulator are proposed. The non-reciprocal phase shift (NRPS) of GaAs/Ce:YIG waveguides with different geometric structures are calculated using numerical simulation. The isolators achieve 35 dB isolation bandwidths greater than 53.5 nm and 70 nm at 1550 nm, with total insertion losses of 2.59 dB and 2.25 dB, respectively. A multi-mode interferometric (MMI) coupler suitable for these two structures is proposed. In addition, suitable manufacturing processes are discussed based on the simulated process tolerances.

A non-resonant photoacoustic effect-based ozone (O ₃ ) gas sensor has been developed, with the potential for O ₃ concentration monitoring in various fields, including the semiconductor industry, water treatment, and O ₃ environmental science research. This sensor comprises a micro-electromechanical system (MEMS) emitter, a miniature photoacoustic cell, a MEMS microphone, and a circuit. By establishing a three-dimensional model and simulating the impact of structural parameters on sensor performance, this comprehensive approach successfully determined the optimal structural parameters. The sensor has a footprint of approximately 12 mm×12 mm ×5 mm (L×W×H), which is 10% of the size of traditional non-dispersive infrared gas sensors. The sensor achieves an accuracy of ±50 ppm within an O ₃ concentration range of 0% to 4%. The response time ( t ₁₀₀ ) is 57 s, and the detection limit (LOD) for O ₃ concentration is 36 ppm.