Multi-millijoule Holmium Laser System

Abstract

Researchers at the University of Central Florida have invented an ultrafast Holmium laser system that can generate multi-millijoule-level laser pulse energy centered at 2.05 µm and a 1 kHz repetition rate. With such capabilities, the laser can produce long, ultra-broad bandwidth (4-12 µm wavelength), mid-IR laser pulses to enable high harmonic generation (HHG) for creating attosecond laser pulses. The pulses are useful for resolving and controlling events in the atto- femto- or pico-second timescales, such as nuclear fusion, biomolecule manipulation, biological imaging or electronic information storage.

Key to the invention is its ability to reduce the required gain by seeding the laser system with microjoule-level energy pulses. For example, after propagating in a dual-stage Ho:YLF crystal in just four passes, the seed pulse is amplified up to a pulse energy of 6 mJ. Thus, the system not only reduces the overall complexities associated with conventional technologies, but it also reduces the amount of gain narrowing. The UCF system is more cost-effective and efficient, as well, since it is water-cooled (versus cryogenically cooled) and incorporates the use of commercially-available lasers.

Technical Details

As an example setup of the UCF Holmium laser system invention, the seed laser may be a Ti:Sapphire and the amplifier may be a chirped-pulse amplifier consisting of a stretcher, an amplification stage, and a compressor. Within the amplification stage is a Holmium gain medium (such as a Ho:YLF crystal with an emission peak centered at 2.05 µm and an absorption peak at 1.94 µm). The stretcher and compressor may include any dispersive optics like diffraction gratings or prisms. For a smaller system footprint, the stretcher and compressor can be a single optical component, such as one formed from chirped volume Bragg gratings (CVBGs) to reflect chirped seed pulses onto the optical component after amplification.

Benefit

Market Application