Single-modulator, dual comb serrodyne spectroscopy.

Dual optical frequency comb spectroscopy allows for high speed, broadband measurements without any moving parts. Here, we combine differential chirp downconversion to probe large spectral bandwidths and serrodyne modulation to separate the positive and negative sidebands in a single modulator. As an initial demonstration, we apply this approach to measure a sharp cavity resonance to illustrate the system performance.

Dual chirped-pulse electro-optical frequency comb method for simultaneous molecular spectroscopy and dynamics studies: formic acid in the terahertz region.

An electro-optic dual-comb system based on chirped-pulse waveforms is used to simultaneously acquire temporally magnified rapid passage signals and normal spectral line shapes from the back-transformation to the time domain. Multi-heterodyne terahertz (THz) wave generation and detection is performed with the difference frequency mixing of two free-running lasers. The method is used to obtain THz spectra of formic acid in the 10 cm to 20 cm (300 GHz-600 GHz) region over a range of pressures.

Difference-frequency chirped-pulse dual-comb generation in the THz region: Temporal magnification of the quantum dynamics of water vapor lines by >60 000.

A new difference-frequency method based on electro-optic phase modulators (EOMs) and two free-running lasers is reported to perform chirped-pulse dual-comb spectroscopy in the THz region. A variation of a near-IR interleaving scheme we recently reported has been developed to interleave the EOMs' orders and sidebands and to map THz comb teeth into the radio-frequency region below 1 MHz. The down-converted comb teeth are shown to have transform limited widths of 1 Hz over a 1 s time scale.

Kilohertz frame rate snapshot hyperspectral imaging of metal reactive materials.

We demonstrate a kilohertz frame rate snapshot hyperspectral imaging system suitable for high-speed imaging, which we name snapshot hyperspectral imager for emission and reactions (SHEAR). This system splits the sensor of a single high-speed camera to simultaneously capture a conventional image and a spectrally sheared response of the scene under study. Given the small, point-source-like nature of burning metal micro-particles, the spectral response of the species is captured without the need for a slit, as is needed in conventional imaging spectrometers.

Optical coherence tomography using physical domain data compression to achieve MHz A-scan rates.

The three-dimensional volumetric imaging capability of optical coherence tomography (OCT) leads to the generation of large amounts of data, which necessitates high speed acquisition followed by high dimensional image processing and visualization. This signal acquisition and processing pipeline demands high A-scan rates on the front end, which has driven researchers to push A-scan acquisition rates into the MHz regime. To this end, the optical time-stretch approach uses a mode locked laser (MLL) source, dispersion in optical fiber, and a single analog-to-digital converter (ADC) to achieve multi-MHz A-scan rates.

A minimally invasive lens-free computational microendoscope.

Ultra-miniaturized microendoscopes are vital for numerous biomedical applications. Such minimally invasive imagers allow for navigation into hard-to-reach regions and observation of deep brain activity in freely moving animals. Conventional solutions use distal microlenses.

Widefield compressive multiphoton microscopy.

A single-pixel compressively sensed architecture is exploited to simultaneously achieve a 10× reduction in acquired data compared with the Nyquist rate, while alleviating limitations faced by conventional widefield temporal focusing microscopes due to scattering of the fluorescence signal. Additionally, we demonstrate an adaptive sampling scheme that further improves the compression and speed of our approach.

High-speed all-optical Haar wavelet transform for real-time image compression.

We present a high-speed single pixel flow imager based on an all-optical Haar wavelet transform of moving objects. Spectrally-encoded wavelet measurement patterns are produced by chirp processing of broad-bandwidth mode-locked laser pulses. A complete wavelet pattern set serially illuminates the object via a spectral disperser.

Wavelength multicasting through four-wave mixing with an optical comb source.

Based on four-wave mixing (FWM) with an optical comb source (OCS), we experimentally demonstrate 26-way or 15-way wavelength multicasting of 10-Gb/s differential phase-shift keying (DPSK) data in a highly-nonlinear fiber (HNLF) or a silicon waveguide, respectively. The OCS provides multiple spectrally equidistant pump waves leading to a multitude of FWM products after mixing with the signal. We achieve error-free operation with power penalties less than 5.

Ultrawideband compressed sensing of arbitrary multi-tone sparse radio frequencies using spectrally encoded ultrafast laser pulses.

We demonstrate a photonic system for pseudorandom sampling of multi-tone sparse radio-frequency (RF) signals in an 11.95-GHz bandwidth using <1% of the measurements required for Nyquist sampling. Pseudorandom binary sequence (PRBS) patterns are modulated onto highly chirped laser pulses, encoding the patterns onto the optical spectra.

High-speed flow microscopy using compressed sensing with ultrafast laser pulses.

We demonstrate an imaging system employing continuous high-rate photonically-enabled compressed sensing (CHiRP-CS) to enable efficient microscopic imaging of rapidly moving objects with only a few percent of the samples traditionally required for Nyquist sampling. Ultrahigh-rate spectral shaping is achieved through chirp processing of broadband laser pulses and permits ultrafast structured illumination of the object flow. Image reconstructions of high-speed microscopic flows are demonstrated at effective rates up to 39.