Sixty years since the birth of nonlinear optics, parametric frequency conversion continues to drive new discovery in ultrafast science, from quantum information to relativistic and high-field physics. However, many standard features of nonlinear optical wave mixing physics continue to limit efficiency and bandwidth in optical frequency conversion, creating barriers to capability and leading to greater complexity in laser architectures used for ultrafast science. I will report on two recent approaches to optical frequency conversion that employ ways to 'trick' nonlinear optical systems into modes of evolution that can avoid the normal limiting behaviors. 

One approach tackles the inefficiency of optical parametric amplification (OPA). OPA efficiency is fundamentally limited by its cyclic evolution behavior, which creates inefficient, asynchronous spatiotemporal conversion due to the local dependence of the conversion cycle on the field intensity. Using a new approach of hybridized nonlinear parametric processes in an ordinary OPA crystal using birefringent phase matching, we have achieved a mid-infrared parametric amplifier with 44% pump-to-signal conversion efficiency and high single-stage gain of 48 dB, while using a Gaussian-like pump spatiotemporal intensity profile. Our method uses simultaneously phase matched OPA and second harmonic generation phase matched at the idler wavelength to enhance the signal conversion efficiency via suppressed back-conversion while preserving the idler energy in a coherent copropagating field at twice its frequency. This “hybridized parametric amplification (HPA)” approach is a promising high-efficiency alternative to ordinary OPA.

A second approach tackles the limited bandwidth of parametric down-conversion devices that can be used to translate ultrafast sources to longer wavelength, while simultaneously offering a new approach to octave-spanning dispersion management. Our approach combines the paradigm of chirped quasi-phase matching for pulse shaping during frequency conversion with the robust, efficient, octave-spanning capability of an adiabatic frequency downconversion device. The result is a simple, monolithic device that can produce an octave-spanning infrared pulse with tailored dispersion – a technique that may be especially convenient for high-energy amplifier chains employing difference frequency generation and/or parametric amplification stages. We have demonstrated a first device with flat group delay versus frequency, allowing efficient conversion of a few-cycle near-infrared input to a near-single-cycle mid-infrared output of the same duration (~12 fs, with bandwidth spanning 2.0-4.0 microns).

BIO:

Jeff Moses is Associate Professor of Applied & Engineering Physics at Cornell University, where he leads the Ultrafast Phenomena and Technologies Group. Prior to that he was a research scientist at the Research Laboratory of Electronics, MIT. He has received the United States NSF CAREER award and was an Air Force Office of Scientific Research Young Investigator.