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Solid-state deep ultraviolet 193nm vortex beam | Adv. Photon. Nexus

Author:

Advanced Photonics Nexus2025, Issue 2 Paper:

Zhang Zhitao, Wang Xiaobo, Wang Junwu, Chen Sheng, Wang Xiaojie, Tong Chen, Li Zheng, Xuan Hongwen, “Compact Narrow-linewidth Solid-state 193 nm Pulsed Laser Source Using Optical Parametric Amplifier and its Vortex Beam Generation”, Adv. Photon. Nexus 4, 026011 (2025)

Deep ultraviolet lasers, with their high photon energy and short wavelength characteristics, have irreplaceable application value in many fields, such as semiconductor lithography, high-resolution spectroscopy, precision material processing, and quantum technology. Compared with excimer lasers and gas discharge lasers, deep ultraviolet solid-state lasers have advantages in coherence and energy consumption. In addition, deep ultraviolet vortex beams carrying orbital angular momentum (OAM) have potential applications in quantum communication and optical micromanipulation. Deep ultraviolet vortex beams, combining the unique physical properties of short wavelength, high resolution, and OAM, are expected to promote innovative development in fields such as micro-nano processing, quantum communication, and super-resolution imaging.

Recently, Xuan Hongwen's research group at the Guangdong-Hong Kong-Macao Greater Bay Area Aerospace Information Research Institute adopted a more compact optical parametric amplification (OPA), frequency doubling, and frequency mixing scheme to extend the near-infrared fundamental frequency light to the 193 nm deep ultraviolet band. A spiral phase plate was also introduced to convert the Gaussian beam into a vortex beam, and the characteristics of this vortex light were transferred to the generated 193 nm deep ultraviolet laser based on the above frequency conversion process, realizing the cross-band transmission of OAM from near-infrared to deep ultraviolet. This research result is titled:Compact Narrow-linewidth Solid-state 193 nm Pulsed Laser Source Using Optical Parametric Amplifier and its Vortex Beam Generationpublished inAdvanced Photonics NexusIssue 2, 2025.

The team used a self-built Yb:YAG bulk material crystal amplified laser (1030 nm) as the fundamental frequency light source. Through OPA and fourth-harmonic generation (FHG), 1553 nm and 258 nm lasers were generated respectively. Then, a 193 nm laser was generated by cascaded sum-frequency generation (SFG) in two LBO crystals. The specific generation principle is shown in Figure 1. The average power of the fundamental frequency light is 14 W, the repetition frequency is 6 kHz, and the pulse width is 13.1 ns. The average power of the finally generated 221 nm laser is 270 mW, and the laser power conversion efficiency from 258 nm to 221 nm is close to 23%; the average power of the generated 193 nm laser is 70 mW, the laser power conversion efficiency from 221 nm to 193 nm is 25%, and the linewidth of the 193 nm laser is 880 MHz. This is shown in Figure 2.

Figure 1 Schematic diagram of the generation path of the 193 nm solid-state deep ultraviolet laser

Figure 2 Relationship between the power and conversion efficiency of the 221 nm and 193 nm lasers and the pump power during the sum-frequency generation process

Subsequently, the researchers inserted a spiral phase plate into the OPA output optical path to convert the Gaussian beam of the 1553 nm laser into a Laguerre-Gaussian mode vortex beam. After readjusting the pump spot parameters, this vortex mode was finally transferred to the generated deep ultraviolet laser; the specific conversion path is shown in Figure 3. Due to the orbital angular momentum transfer law of vortex light, the orbital angular momentum of the generated 221 nm laser remains consistent with that of the 1553 nm laser, which is still 1, while the orbital angular momentum of the 193 nm laser becomes 2 after superposition. This was verified by converting the beam into a Hermite-Gaussian beam using a cylindrical lens, as shown in Figure 4.

Figure 3 Schematic diagram of the experimental principle of 193 nm vortex light generation

Figure 4 Schematic diagram of the mode transformation of 1553 nm, 221 nm, and 193 nm lasers

This work has made important progress in deep ultraviolet laser generation technology, light field control, and application expansion, providing new tools for multiple fields and having strong application value. At the same time, it has also promoted cross-innovation of related technologies and enhanced the practical value and scientific connotation of deep ultraviolet solid-state lasers.

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