Ultra Photonics
Research Group

We study novel ultrafast nonlinear dynamics in photonic structures, and incorporate the dynamics to enhance the device performances with focuses on sensing and imaging applications.


Graduate Research Assistant Neeraj Prakash has been awarded the 2021 Laser Congress Best Poster Award. Congratulations, Neeraj!

Nov 11, 2021

A spinoff from our lab, Poseidon Photonics, has been granted $100k funding from the Colorado OEDIT to commercialize the CANDi laser technology.

Nov 4, 2021

Summer Intern Jesse Duran is featured on the CU Boulder Today. Congratualtions, Jesse!

Aug 31, 2021

Our paper, Time-magnified photon counting with a 550-fs resolution, is published on Optica. Congratulations, Bowen, Jan, and Yijun!

Aug 16, 2021

Graduate Research Assistant Jan Bartos has been awarded the 2021 ED Graduate Assistance in Areas of National Need. Congratulations, Jan!

July 31, 2021


We study novel ultrafast nonlinear dynamics in photonic structures, and incorporate the dynamics to enhance the device performances with focuses on sensing and imaging applications. We are also interested in functional integration of photonic devices with microfluidic, MEMS, photopolymer, and 2D materials to broaden the scope of chip-scale sensing and imaging devices.



Time-magnified photon counting with a 550fs resolution

The authors demonstrate a quantum temporal magnifier that enables femtosecond time-resolved photon counting with close-to-unity efficiency for the first time. The new technology can benefit many research fields such as fluorescence lifetime microscopy, time-of-flight imaging, light-in-flight imaging, time-gated Raman spectroscopy, and computational diffuse optical tomography.

arXiv 2021

Deterministic generation of parametrically driven dissipative Kerr soliton

The authors study the nature of parametrically driven dissipative Kerr soliton (PD-DKS) in a doubly resonant degenerate micro-optical parametric oscillator with the cooperation of χ(2) and χ(3) nonlinearities. Benefiting from the low complexity and wavelength down-conversion of PD-DKS, the working principle can be applied to different material platforms as a competitive field-deployable ultrashort pulse and broadband frequency comb source architecture at the mid-infrared molecular fingerprinting spectral range.

Nanophotonics 2021

Photonic Flywheel in a Monolithic Fiber Resonator

The authors devise a novel two-step pumping scheme for dissipative Kerr soliton generation at the quantum-noise limit, achieving the first compact photonic flywheel with sub-femtosecond time jitter. The scheme can be generalized to various device platforms for the long-sought-after goal of a field-deployable precision metrology device in both spectral and time domains.

Physical Review Letters 2020

Bidirectional mode-locked all-normal dispersion fiber laser

The authors present the first bidirectional all-normal-dispersion fiber laser based on nonlinear polarization rotation. With favorably flat-top spectra spanning more than 5 THz and exceedingly high output pulse energies greater than 1 nJ in both directions, our work paves the way for a new class of energetic bidirectional mode-locked fiber lasers that will benefit precision optical metrologies including dual-comb applications in both linear and nonlinear regimes.

Optica 2020

Gate-tunable frequency combs in graphene–nitride microresonators

The authors demonstrate the gated intracavity tunability of graphene-based optical frequency combs, by coupling the gate-tunable optical conductivity to a silicon nitride photonic microresonator, thus modulating its second- and higher-order chromatic dispersions by altering the Fermi level. This realization of a charge-tunable graphene heterostructure for controllable frequency combs and soliton dynamics opens a new architecture at the interface of single-atomic-layer nanoscience and ultrafast optoelectronics.

Nature 2018

Panoramic-reconstruction temporal imaging for seamless measurements of slowly-evolved femtosecond pulse dynamics

The authors demonstrate a panoramic-reconstruction temporal imaging (PARTI) system that uniquely integrates the ultrafast temporal magnifier and the mosaic image stitching technologies. PARTI enables the studies of important optical nonlinear dynamics where not only fine temporal details but also long evolution information are necessary for the comprehensive understanding of the phenomena.

Nature Communications 2017

A broadband chip-scale optical frequency synthesizer at 2.7 × 10−16 relative uncertainty

The authors report the first fully stabilized CMOS-compatible chip-scale Kerr microcomb. Comparing 46 microcomb lines with a state-of-the-art fiber laser frequency comb, the authors measure an unprecedented microcomb tooth-to-tooth relative frequency uncertainty down to 50 mHz and 2.7×10−16. It is a promising scalable platform for coherent Raman spectroscopy, high-precision optical clockwork, high-capacity coherent communications, arbitrary waveform generation, and astrophysical spectrography.

Science Advances 2016

High-energy pulse synthesis with sub-cycle waveform control for strong-field physics

The authors address the challenges of sub-cycle optical pulse generation and establish a novel light source architecture by multispectral coherent synthesis of optical parametric chirped pulse amplifiers. It enables new light-matter interaction studies and applications beyond the slowly varying envelope approximation, providing a way to gather data of unprecedented detail about how individual molecules interact during chemical reactions, with ramifications for not only the basic sciences but chemical engineering and pharmaceutical research as well.

Nature Photonics 2011