High Energy and Average Power Femtosecond Er:ZBLAN Fiber Lasers Operating in Mid-IR Spectral Range (Univ. Of Michigan)
Abstract
Mid-IR spectral range is important for many scientific and technological applications in chemical sensing, medical surgery, attosecond science, directed energy, etc.. However, there is lack of laser sources operating directly in this range, particularly practical laser gain media compatible with direct laser diode pumping and capable of producing high pulse energies. There are evenfewer options for direct generation of high-energy ultrashort pulses in mid-IR. Therefore,accessing this spectral range with high-energy ultrashort pulses is currently based on optical parametric wavelength down-conversion, which exploits laser sources available at shorter optical wavelengths, but with significantly reduced efficiency, increased system complexity, sizeand cost. Fluoride glass rare-earth doped fiber lasers offer a new technological pathway into mid-IR, with potential of very practical (compact and efficient) laser systems for generating high-energy ultrashort pulses directly in mid-IR. There are multiple fiber-laser options for different wavelengths in the range from 2 m to 4 m. Particularly interesting are Er:ZBLAN fibers. Theycan be pumped at 975 nm the telecom pumr:ZBLAN offers high efficiency, double the quantum defect due to one-to-two pump-to-signal conversionin this medium. Mid-IR signal is at 2.75 m, with 35% slope efficiency and with output powers up to 42 W demonstrated. It is also possible to pump this fiber laser with a combination of 975 nm and 1.97 m pump wavelengths (obtainable, for example, using Tm:doped fiber lasers), in which case the laser will operate at 3.68 m. The important advantage of these Er:ZBLAN fibersis that they are readily available commercially with various core-size options, and from differentvendors. As a result there have been several recent demonstrations of these lasers operating in CW, Q-switched long pulse, and mode-locked ultrashort pulse oscillator regimes, which established the feasibility of efficient high power operation, potential for high energies, as well as compatibility of this medium with femtosecond pulse generation. However, so far there has been no significant efforts to explore generation and amplification of ultrashort high-energy pulses with Er:ZBLAN optical fibers. It is also important to emphasize that ZBLAN glass based fibers are much more difficult to fusion-splicing integrate into monolithic all-fiber subsystems due to the much lower melting temperature of these glasses compared to the standard fused silica, and technological efforts of developing such a ZBLAN-compatible technology arecurrently in the early stages. We are proposing a research program which would explore the key aspects of generating high energy ultrashort pulses in the mid-IR wavelength range using Er:ZBLAN fibers (or potentially,other types of fiber-glass and corresponding rare-earth dopants for mid-IR). We envision thisprogram to proceed in the two main stages. During Stage I we would focus on achieving high energy (in the multiple-mJ to ~10mJ range) from Er:ZBLAN fibers with relatively short 1 100 ns pulses, and then applying 2 chirped pulse amplification (CPA), and coherent pulses stacking amplification (CPSA) to demonstrate femtosecond multi-millijoule pulses in the mid-IR. This stage would als towards much higher ultrashort pulse energies by demonstrating coherent spatial combining of multiple parallel ZBLAN-glass based fiber laser channels, combining such systems with the previously demonstrated CPA and CPSA approaches. Success of this stage would heavily depend on the availability of sufficiently developed fusion-splicing techniques for ZBLAN glass fibers.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 08, 2020
- Source ID
- N000142012286
Entities
People
- Almantas Galvanauskas
Organizations
- Board of Regents of the University of Michigan
- Office of Naval Research
- United States Navy