Jonathan R. Birge

Two-dimensional spectral shearing interferometry for few-cycle pulse characterization.

We present a new method for measuring the spectral phase of ultrashort pulses that utilizes spectral shearing interferometry with zero delay. Unlike conventional spectral phase interferometry for direct electric-field reconstruction, which encodes phase as a sensitively calibrated fringe in the spectral domain, two-dimensional spectral shearing interferometry robustly encodes phase along a second dimension. This greatly reduces demands on the spectrometer and allows for complex phase spectra to be measured over extremely large bandwidths, potentially exceeding 1.5 octaves.

Self-Referenced 200 MHz Octave-Spanning Ti:Sapphire Laser with 50 Attosecond Carrier-Envelope Phase Jitter

Carrier-envelope phase stabilization of a 200MHz octave-spanning Ti:sapphire laser without external broadening is demonstrated. The individual comb lines spaced by 200MHz can conveniently be resolved using commercial wavemeters. The accumulated in-loop carrier-envelope phase error (integrated from 2.5 mHz to 10 MHz) using a broadband analog mixer as phase detector is 0.117 rad, equivalent to 50 attosecond carrier-envelope phase jitter at 800 nm.

Low-cost, single-mode diode-pumped Cr:Colquiriite lasers

We present three Cr3+:Colquiriite lasers as low-cost alternatives to Ti:Sapphire laser technology. Single-mode laser diodes, which cost only

9.3: High Contrast Color Splitting Architecture Using Color Polarization Filters

150 each, were used as pump sources. In cw operation, with approximately 520 mW of absorbed pump power, up to 257, 269 and 266 mW of output power and slope efficiencies of 53%, 62% and 54% were demonstrated for Cr:LiSAF, Cr:LiSGaF and Cr:LiCAF, respectively. Record cw tuning ranges from 782 to 1042 nm for Cr:LiSAF, 777 to 977 nm for Cr:LiSGaF, and 754 to 871 nm for Cr:LiCAF were demonstrated. In cw mode-locking experiments using semiconductor saturable absorber mirrors at 800 and 850 nm, Cr:Colquiriite lasers produced approximately 50-100 fs pulses with approximately 1-2.5 nJ pulse energies at approximately 100 MHz repetition rate. Electrical-to-optical conversion efficiencies of 8% in mode-locked operation and 12% in cw operation were achieved.

Visible wavelength astro-comb

A high performance color management architecture is presented for the projection of liquid crystal on silicon microdisplays. Based on ColorLinks ColorSelect™ polarization filter technology, and used in conjunction with polarizing beamsplitters, the system gives excellent performance with black to white contrast >500, transmission >50% and standard primary color coordinates at f/2.5. Low cost polarizing beamsplitters can be used without significant performance degradation placing this ColorQuad™ architecture in the forefront of future three panel projection systems.

Nonintrusive phase stabilization of sub-two-cycle pulses from a prismless octave-spanning Ti:sapphire laser.

We demonstrate a tunable laser frequency comb operating near 420 nm with mode spacing of 20-50 GHz, usable bandwidth of 15 nm and output power per line of ~20 nW. Using the TRES spectrograph at the Fred Lawrence Whipple Observatory, we characterize this system to an accuracy below 1m/s, suitable for calibrating high-resolution astrophysical spectrographs used, e.g., in exoplanet studies.

Chirally-coupled-core Yb-fiber laser delivering 80-fs pulses with diffraction-limited beam quality warranted by a high-dispersion mirror based compressor

Carrier-envelope (CE) phase-stabilized sub-two-cycle pulses are generated from a 500 MHz compact prismless octave-spanning laser without extracavity nonlinear optical processes distorting the laser output. The necessary f and 2f spectral components are generated intracavity and coupled out independently from the main pulse through specially designed cavity mirrors, resulting in a 55 dB CE beat note (100 kHz resolution bandwidth). The in-loop CE phase error (integrated from 2.5 mHz to 10 MHz) is 67 mrad, equivalent to a timing jitter between carrier and envelope of 28 as at 790 nm.

Ultrabroadband beam splitter with matched group-delay dispersion

We demonstrate a high-energy femtosecond laser system that incorporates two rapidly advancing technologies: chirally-coupled-core large-mode-area Yb-fiber to ensure fundamental-mode operation and high-dispersion mirrors to enable loss-free pulse compression while preserving the diffraction-limited beam quality. Mode-locking is initiated by a saturable absorber mirror and further pulse shortening is achieved by nonlinear polarization evolution. Centered at 1045 nm with 39-MHz repetition rate, the laser emits 25-nJ, positively chirped pulses with 970-mW average power. 6 bounces from double-chirped-mirrors compress these pulses down to 80 fs, close to their transform-limited duration. The loss-free compression gives rise to a diffraction-limited optical beam (M2 = 1.05).

Diode-pumped passively mode-locked GHz femtosecond Cr:LiSAF laser with kW peak power

We present a general design strategy for a broadband thin-film beam splitter with matched group-delay dispersion. By taking the substrate dispersion into account in the coating design, any combination of input and output can show the same dispersion for transmission and reflection. As a specific implementation, an ultrabroadband 50:50 beam splitter from 600to1500?nm for femtosecond laser applications was designed, fabricated, and characterized.

Efficient optimization of multilayer coatings for ultrafast optics using analytic gradients of dispersion.

We report a single-mode diode-pumped, passively mode-locked Cr:LiSAF laser with gigahertz (GHz) repetition rate and kilowatt peak power. A low-loss saturable Bragg reflector with low modulation depth and optimized dispersion compensation mirrors enables the generation of stable, cw mode-locked, sub-100-fs pulses at 1 GHz repetition rate around 865 nm when pumping with four or six laser diodes. Using a 0.25% output coupler and a total absorbed pump power of 0.9 W from six laser diodes, 55 fs, 110 pJ pulses are produced. This corresponds to 1.8 kW of peak power, which to our knowledge represents a record result for GHz Cr:colquiriite lasers.