5. Solid State Laser Development

5. Solid State Laser Development

Compact and simple CW seeded OPA for generating high power picosecond pulses in the 2-4 um wavelength region. The OPA is pumped by the Nd:YLF regenerative amplifier and works with 45 % of idler + signal conversion efficiency.

The experimental studies of the ultrafast phenomena performed in the research group require table top laser systems that are at the frontier of today’s laser technology. We try to push limits in terms of ultrashort pulse’s peak power, duration and tunability with simultaneous control of its optical phase and amplitude. Since the lasers are used in actual experiments to induce nonlinear effects and probe fine features of the quantum dynamics, special care is taken to ensure their short and long term stability to increase signal to noise ratio and avoid measuring artifacts.   

Over the years, the group has accumulated considerable laser expertise.  A number of developments currently in use in commercial lasers, from electro-optics to HV high speed drivers used in pockel cells for regenerative amplifiers, trace their roots to our group.  Through a collaborative research program with Lumonics, a number of laser systems and optical systems have been commercialized.  You have a 70% chance of flying on aircraft in which the many kms of aerospace wiring was marked by our laser systems to avoid wiring mistakes and to reduce risk of on board electrical fires.  Intel has used our lasers in high density packaging.  The group has also developed the first laser system to achieve the long held promise of attaining the fundamental (single cell) limit to minimally invasive surgery – and first method capable of surgery without scar tissue formation (see Innovation). 

This technical expertise in laser source development has enabled the group to explore new domains, to go beyond the constraints of commercially available systems. In fact, the major emphasis is to develop new lasers to do experiments not possible with commercial systems.   We define the experiments of interest – not the laser.

“IR Death Laser”

The current project in laser source development is aimed at the development of a 100 W class tunable femtosecond mid-IR laser.  The scientific objectives are to provide a high enough peak power system in the IR that it will be possible to directly image the light-matter interaction at the atomic level using fs electron diffraction.  We will soon be able to tune into a specific vibrational mode and drive it via overtones into highly anharmonic regimes in the many body potential to directly observe the coupling to other modes.  At this level of excitation, we will be able to see highly nonclassical interference effects to dispel the notion of nuclear motions within ball and spring depictions.  We need to understand the spatial correlation of such interference to understand how chemistry reduces to a few key, localized, modes.

To achieve this goal, the target of this project is the development of a high energy (> 60 mj per pulse) and broadband tunable (3 – 12 μm) laser source. This laser source is going to deliver ultrafast laser pulses with pulse durations of about 100 fs, which will be combined with new pulse shaping technology in the IR be shaped to effectively any arbitrary transform of the input spectrum, as dictated by desired control over atomic motions.

Due to the lack of laser active media that can be used to generate broadband Mid-IR radiation, the approach of this project is to use optical parametric amplification schemes to convert and amplify the broadband target wavelength. This project also includes the development of a high power Holmium based laser that efficiently pumps a new class of non-linear crystals within OPA stages specifically optimized for performance at 2 µm.

This laser source has the potential to coherently drive atomic motions far enough from equilibrium to be directly observed using femtosecond electron diffraction and opens up a new window in probing far from equilibrium nuclear motions critical to understanding structural transitions.  It is also expected this new power class of high power mid-IR lasers will have important medical applications (see below) that promise to reach high enough powers to surpass mechanical tool speeds in surgery.