High Energy, Long Pulse Laser (Multispectral line long pulse solid state laser)

Period of Performance: 07/08/2003 - 07/08/2005

$750K

Phase 2 SBIR

Recipient Firm

Light Age, Inc.
SOMERSET, NJ 08873
Principal Investigator

Abstract

The design of a laser system with simultaneous requirements of multiple output wavelengths, long pulse duration, and high output energy, is at best challenging. This challenge has been met during Phase I of this program. The focus of Phase II is on making the system more compact, and on increasing the output energy. Multi-wavelength lasing, although not always efficient with some laser systems because of phase-matching requirements that depend on the emitted wavelength, is generally accomplished by second and/or third harmonic generation of the fundamental emission. For wavelengths that are longer than the fundamental, Raman conversion or Optical Parametric Oscillation is the process that is usually chosen. Both of these optical processes are non-linear in nature, and therefore require high peak powers. These power levels are typically achieved with a short pulse laser system using either Q-switching, and/or mode-locking. Achieving high output energies, with long pulses that can vary from hundreds of nanoseconds to several milliseconds, is however a more difficult task. At the completion of Phase I, we have demonstrated just that, leveraging on various proprietary technologies developed by Light Age, Inc. Light Age uses alexandrite crystals as the laser gain medium. These lasers are all solid state, quasi-four level vibronic sources, and therefore tunable. Light Age leverages the unique optical properties of alexandrite and its proprietary pulse stretching technology to produce laser output with pulse durations of 500 to 5000 ns. In order to reach peak powers needed for nonlinear conversion, the laser output is amplified in a chain of alexandrite amplifier stages. The combination of alexandrite's high damage threshold and excellent capacity to store energy (far exceeding other solid state materials) makes alexandrite very well suited for producing extremely high output energies. After the amplification of the pulse-stretched alexandrite laser, a high peak power beam is generated that is suitable for nonlinear frequency conversion. The alexandrite laser combined with Light Age's high efficiency Raman conversion techniques allows for tunable laser radiation throughout the visible and near IR. Multispectral output is achieved using the combination of these technologies with harmonic generation. The development of a multispectral line long pulse laser source greatly enhances Light Age's laser technology and allows us to increase our position in a few markets and enter into many new markets. Many of these applications will benefit from one or more of the otherwise hard to achieve laser specifications. The markets we expect to address with this technology are: 1) The production of holograms using a three color coherent output of the laser source. Holograms created using pulse laser sources reduce much of the complexity of stabilizing the object since the hologram can be produced with a single laser pulse in the hundreds of nanosecond durations. 2) Medical diagnostic is utilizing lasers in order to detect early stage cancers and other abnormalities throughout the body. These lasers can be used to excite fluorescent contrast agents or be used in photoacoustic imaging. The wavelength range in the fundamental of alexandrite's tuning curve is ideal for deep penetration into tissue making it an ideal source for medical diagnostics. 3) Selective laser trabeculloplasty for the treatment of glucoma. Laser pulses of 1-10 ms may have an advantage in preserving the integrity of the trabecular meshwork. Due to the versatility of the pulse stretched, high energy alexandrite laser, we expect that many applications will be developed or enhanced by this laser source. These developments will allow some of early stage research applications to mature into larger commercial markets.