Alex Lind

Photonic-Chip Supercontinuum with Tailored Spectra for Counting Optical Frequencies

Supercontinuum generation using chip-integrated photonic waveguides is a powerful approach for spectrally broadening pulsed laser sources with very low pulse energies and compact form factors. When pumped with a mode-locked laser frequency comb, these waveguides can coherently expand the comb spectrum to more than an octave in bandwidth to enable self-referenced stabilization. However, for applications in frequency metrology and precision spectroscopy, it is desirable to not only support self-referencing, but also to generate low-noise combs with customizable broadband spectra. In this work, we demonstrate dispersion-engineered waveguides based on silicon nitride that are designed to meet these goals and enable precision optical metrology experiments across large wavelength spans. We perform a clock comparison measurement and report a clock-limited relative frequency instability of

Photonic-chip Waveguides for Supercontinuum Generation with Picojoule Pulses

3.8\times10^{-15}

High-harmonic generation in periodically poled waveguides

at

On-chip waveguides for self-referencing low-power and high-repetition-rate laser frequency combs

\tau = 2

Molecular fingerprinting with bright, broadband infrared frequency combs

seconds between a 1550 nm cavity-stabilized reference laser and NISTs calcium atomic clock laser at 657 nm using a two-octave waveguide-supercontinuum comb.

Dual frequency comb spectroscopy in the molecular fingerprint region

We employ numerical simulations to design tapered silicon nitride waveguides for broadband supercontinuum generation from low-energy femtosecond pulses and multi-section waveguides for broadening of picosecond pulses.

Ultrabroadband Supercontinuum Generation and Frequency-Comb Stabilization Using On-Chip Waveguides with Both Cubic and Quadratic Nonlinearities

Optical waveguides made from periodically poled materials provide high confinement of light and enable the generation of new wavelengths via quasi-phase-matching, making them a key platform for nonlinear optics and photonics. However, such devices are not typically employed for high-harmonic generation. Here, using 200-fs, 10-nJ-level pulses of 4100 nm light at 1 MHz, we generate high harmonics up to the 13th harmonic (315 nm) in a chirped, periodically poled lithium niobate (PPLN) waveguide. Total conversion efficiencies into the visible--ultraviolet region are as high as 10 percent. We find that the output spectrum depends on the waveguide poling period, indicating that quasi-phase-matching plays a significant role. In the future, such periodically poled waveguides may enable compact sources of ultrashort pulses at high repetition rates and provide new methods of probing the electronic structure of solid-state materials.

Self-Seeded Mid-Infrared Generation in Periodically-Poled Lithium Niobate Waveguides

Using silicon nitride and aluminum nitride chip-integrated waveguides, we demonstrate supercontinuum spanning 500-4000 nm. We detect the carrier-envelope-offset frequency using total optical power below 15 mW, or, alternatively, directly from the waveguide output.