Novel Stabilization Scheme for Obtaining Single Longitudinal Mode (SLM) Radiation from a Pulsed Nd:Yag laser

Background: Pulsed, q-switched solid-state lasers are an almost ubiquitous light source for powerful, short laser pulses, as used in industry and research labs. Typically, a simple free running cavity design is employed, while more demanding applications require seeded lasers. In that case a narrow bandwidth beam is introduced into the cavity of the host laser. The wavelength of the CW laser is adjusted to coincide with the fluorescence maximum of the gain material of the host. When the CW laser is resonant with one of the cavity modes of the host, this mode will win the mode competition for the population inversion in the gain material with regard to the other longitudinal modes present in the free running host laser. When the host laser is seeded, the bandwidth produced is reduced dramatically. In the case of Nd:YAG, the width of the fluorescence maximum at 1064 nm is ~ 20 GHz, while the bandwidth of a seeded Nd:YAG laser with a pulse duration of 8 ns is typically 0.1 GHz, a reduction of a factor 200. The narrow bandwidth is required for applications in spectroscopy, and for pumping narrow bandwidth Optical Parametric Oscillators. Similarly the coherence length of these light pulses increases from ~ 1.5 cm to 3 meter, which is important for coherent detection schemes, such as coherent Lidar, and CARS. The seeded lasers also show superior pulse characteristics. In free running q switched lasers each pulse is modulated by beating between the longitudinal modes generated in the cavity. Because of the random nature of these modes, each consecutive pulse shows a different shape. The free running modes are built up from the vacuum background, the time required to build up a mode is also subject to random behavior, causing jitter in the timing of the generated pulse. In seeded lasers the pulse is built up from the injected radiation, eliminating the random behavior. The generated radiation only contains one longitudinal mode and as a result no beating artifacts. Technology: University researchers have developed a novel method of generating an electronic feedback signal to stabilize the length of an optical cavity. This can be used for seeding such a cavity, generating radiation with a much smaller bandwidth and much larger coherence length. Application: This invention can be used for manufacturing new, cheaper lasers or retrofitting less expensive lasers to match the performance characteristics of more expensive laser systems.

Type of Offer: Licensing



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