Power-scalable Optical System for Nonlinear Frequency Conversion

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This patent describes a power-scalable optical system for nonlinear frequency conversion, particularly suited for converting high-power laser light to different wavelengths (such as frequency doubling, halving, or parametric down-conversion). The core component is a thin, disk-shaped nonlinear birefringent crystal with specialized high-reflective and partially-reflective coatings. These coatings, combined with an efficient heat sink, enable resonant intensity enhancement for both the incoming and frequency-shifted beams and maintain optimal phase relationships for maximum conversion efficiency. This architecture allows for efficient frequency conversion without being limited by thermal or optical damage, which traditionally cap the output power of such systems.

Use CasesContent extracted from patent full text and abstract with AI.

• Industrial laser processing, such as precision welding of highly reflective materials (e.g., copper) using visible light generated by frequency doubling.
• Scientific and medical laser sources requiring high-power, wavelength-specific beams in the visible and infrared ranges.
• High-power, single-frequency laser systems for spectroscopy, metrology, or quantum optics experiments.
• Optical parametric oscillator (OPO) setups for generating widely tunable laser output across various spectral regions.
• Laser systems requiring robust, power-scalable solutions for frequency conversion (e.g., frequency doubling, halving, or down-conversion).
• Fiber laser communications or materials processing applications that benefit from efficient wavelength conversion and power scaling.
• Mode-locked lasers with high repetition rates enabled by frequency-specific cavity design.

BenefitsContent extracted from patent full text and abstract with AI.

• True power scalability: Output power can be increased by scaling beam size at constant intensity, overcoming traditional thermal and damage limits in nonlinear crystals.
• High conversion efficiency: The double-resonant cavity structure enhances both pump and converted intensities, maximizing output.
• Superior thermal management: The design minimizes temperature gradients and phase mismatch issues, allowing stable operation at high powers.
• Enhanced wavelength and single-frequency selectivity: The system also functions as a wavelength (frequency) selective element, enabling single-frequency laser operation.
• Versatile frequency conversion: Applicable to a range of nonlinear processes including frequency doubling, halving, parametric down-conversion, and more.
• Simplified manufacturing: The coating and thin-disk design require less precise thickness control and can be batch-produced.
• Enables advanced control schemes: Supports error-signal based locking (e.g., Hansch-Couillaud) for stable, mode-hop-free operation.
• Applicable intra-cavity or extra-cavity, continuous-wave or pulsed, facilitating flexible system architecture and high-energy pulse generation.

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Patent Abstract

The present invention proposes a system for frequency conversion of a laser pump radiation comprising an optical element for frequency conversion (frequency-doubling, frequency-halving and more generally to parametric down-conversion) of lasers or laser beams with power scalability. The element comprises a nonlinear birefringent crystal in the shape of a thin plate where a pump beam generates frequency-shifted radiations. Phase-matching or quasi-phase matching conditions are fulfilled in the nonlinear crystal between the various beams. The front- and back-side of the nonlinear crystal are provided with a high-reflective (HR) and a partially-reflective (PR) coating, respectively, to obtain intensity enhancement of both the pump and one of the frequency-converted radiations, and to maintain the relative phase delay between the various beams maximizing conversion efficiency. The the nonlinear crystal is contacted preferably through the HR coating to a heat sink minimizing the temperature inhomogeneity in the nonlinear crystal, in particular in transverse direction. The longitudinal heat flow intrinsic in this scheme leads to power scalability. When used intra-cavity, this nonlinear element also acts as a wavelength-selective component that forces the laser to operate on a resonance of the nonlinear element itself, maximizing frequency conversion. Moreover, this wavelength selectivity paves the way to single-frequency operation of high-power lasers with intra-cavity frequency conversion. Throughout this description the initial laser beam being converted in the nonlinear process is denoted as "pump" and/or "pump beam" and/or "pump radiation".