Highly efficient octave-spanning long-wavelength infrared generation with a 74% quantum efficiency in a χ⁽²⁾...

Area of Science:

• Photonics
• Nonlinear Optics
• Materials Science

Background:

• Compact and efficient mid-infrared (MIR) lasers are crucial for spectroscopy and other applications.
• Existing waveguide platforms for MIR supercontinuum and frequency comb generation rely on weak third-order nonlinearities.
• There is a need for more efficient nonlinear optical processes in the MIR spectrum.

Purpose of the Study:

• To propose and demonstrate a novel micrometer waveguide platform for long-wavelength infrared (LWIR) laser generation.
• To achieve high quantum efficiency in LWIR laser generation using a second-order nonlinear (χ(2)) process.
• To explore the potential of this platform for integrated nonlinear photonics in the MIR.

Main Methods:

• Development of a micrometer waveguide platform utilizing a ZnGeP2 crystal.
• Implementation of birefringence phase matching for nonlinear optical interactions.
• Generation of broadband spectra via optical parametric generation (OPG).

Main Results:

• Demonstration of an octave-spanning spectrum from 5-11 μm.
• Achieved a record quantum conversion efficiency of 74% for LWIR single-pass parametric processes.
• Observed a threshold energy of approximately 616 pJ, significantly lower than bulk MIR OPGs.

Conclusions:

• The proposed χ(2) micrometer waveguide platform enables efficient LWIR laser generation.
• This technology offers a significant improvement in quantum efficiency and threshold energy for MIR parametric processes.
• The platform is extendable to other nonlinear crystals, paving the way for new frontiers in MIR integrated nonlinear photonics.