Laser system for generation of high-power sub-nanosecond pulses with controllable wavelength in 2-15 μm region
Inventors
Franjic, Kresimir • Kraemer, Darren • Cowan, Michael L. • Hua, Renzhong • Miller, R. J. Dwayne
Assignees
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Publication Number
US-7630418-B2
Publication Date
2009-12-08
Expiration Date
Abstract
A laser system capable of efficient production of high energy sub-nanosecond pulses in the 2-15 μm spectral region is disclosed. Diode pumped solid state lasers are used as pump sources. The system design is simple, reliable and compact allowing for easy integration. The laser system includes a combination of compact solid-state ˜1 micron laser sources, producing high power picosecond pulses, with optical parametric amplification and a quasi-continuous wave laser for seeding the amplification process that enables the efficient conversion of the high power ˜1 micron laser radiation to tuneable mid-infrared sub-ns pulses. New parametric processes are presented for achieving high gains in bulk nonlinear crystals. Furthermore, a method of exceeding the fundamental conversion efficiency limit of direct three wave mixing is presented. The compact and robust nature of this novel laser system opens up the use of high power and high peak power mid-infrared laser pulses to a wide variety of important medical and dental applications.
Core Innovation
The invention relates to producing high power picosecond mid-infrared (mid-IR) laser pulses having a wavelength λ3 between 2 and 15 μm. It uses optical parametric amplification that generates λ3 through three wave mixing in at least one bulk non-linear optical crystal, and the output pulses are directed from an optical parametric amplifier output to a desired location for use at a target site.
A core aspect is the combination of high energy pump pulses with a low power continuous wave (CW) laser beam in an optical parametric amplifier, while preventing an optical parametric oscillator from being present between the CW beam and the optical parametric amplifier. The pump pulses have wavelength λ1 between about 1 and about 1.1 μm with a pulse duration between about 1 and about 1000 ps and energy larger than about 10 μJ, and the CW laser beam has wavelength λ2 that satisfies the relation 1/λ2 = 1/λ1 − 1/λ3, with λ2 between about 1.19 and 2 μm.
The invention further incorporates optical parametric amplifier architecture using at least one bulk non-linear optical crystal and enables shaping of the spectral and temporal profile of the high energy mid-IR pulses either directly at the mid-IR wavelengths or indirectly through shaping of the CW laser beam before the optical parametric amplifier. A transport means transports the generated high energy mid-IR pulses to a desired location, including an embodiment where the transporting means includes a flexible fibre waveguide.
Claims Coverage
Two independent claims define the invention at the method level and at the laser system level. The inventive coverage centers on combining wavelength-matched pump pulses and a CW seed into one or more bulk-crystal optical parametric amplifiers without an optical parametric oscillator between the CW beam and the optical parametric amplifier, generating mid-IR picosecond pulses by three-wave mixing and then directing, shaping, and transporting the resulting pulses; additional system-level features include spectral/temporal shaping means and mid-IR transport means. Overall, 5 main inventive features are reflected across the two independent claims.
Wavelength-matched pump and CW seed for mid-IR three-wave mixing in a bulk-crystal OPA
Produces high energy picosecond mid-IR pulses with wavelength λ3 between 2 and 15 μm by providing pump pulses with wavelength λ1 between about 1 and about 1.1 μm and a low power continuous wave laser beam with wavelength λ2 satisfying 1/λ2 = 1/λ1 − 1/λ3, directing and combining them with substantial spatial overlap into at least one optical parametric amplifier each having at least one bulk non-linear optical crystal so that high energy picosecond mid-IR pulses are produced through three wave mixing between the spatially overlapped pump pulses and CW laser beam in the bulk non-linear optical crystal.
No optical parametric oscillator between the CW beam and the OPA
Directs and combines the pump pulses and the CW laser beam into at least one optical parametric amplifier without said CW laser beam passing through an optical parametric oscillator before entering said optical parametric amplifier, and with the peak intensity of the pump pulses sufficient such that high energy picosecond mid-IR pulses at wavelength λ3 between 2 and 15 μm are produced through three wave mixing.
Picosecond pump pulse parameters and spatial overlap combining into OPA
Produces high energy pump pulses with wavelength λ1, pulse duration between about 1 and about 1000 ps, and energy larger than about 10 μJ, and directs, focuses and combines the pump pulses and the CW laser beam so that they have substantial spatial overlap prior to directing the combined beams into the optical parametric amplifier.
Shaping spectral and temporal profile of the mid-IR pulses
Shapes the spectral and temporal profile of said high energy mid-IR pulses either directly at said mid-IR wavelengths, or indirectly through the shaping of said CW laser beam before said at least one optical parametric amplifier.
Transporting the generated mid-IR pulses to a desired location
Directs the high energy mid-IR pulses from an output of said at least one optical parametric amplifier to a desired location, including means for transporting the high energy mid-IR pulses at wavelengths λ3 from an output of said at least one optical parametric amplifier to a desired location.
Across the independent claims, the core inventive concept is a wavelength-related pump/CW seed combination into bulk non-linear optical crystal optical parametric amplifiers without an optical parametric oscillator in between the CW beam and the OPA, producing high power picosecond mid-IR pulses through three-wave mixing. Claim 23 additionally requires means to shape the spectral and temporal profile of the mid-IR pulses and means to transport them to a desired location.
Stated Advantages
Produces high energy picosecond mid-IR pulses with wavelength λ3 between 2 and 15 μm through three wave mixing in at least one bulk non-linear optical crystal.
Enables spectral and temporal profile shaping of the high energy mid-IR pulses, either directly at mid-IR wavelengths or indirectly through shaping the CW laser beam.
Provides transport of the generated high energy mid-IR pulses to a desired location, including delivery using a flexible fibre waveguide.
Documented Applications
Impulsive heat deposition (IHD) medical and dental impulsive heat deposition applications are discussed in the provided patent content.
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