Stephen R. Friberg

High powers and subpicosecond pulses from an external‐cavity surface‐emitting InGaAs/InP multiple quantum well laser

We demonstrate that surface‐emitting lasers operating in an external cavity can produce high average powers, high peak powers, and ultrashort pulses. By optical pumping of InGaAs/InP multiple quantum well samples in an external cavity, we generated 190 mW both in continuous and mode‐locked operation at 1.5 μm. Synchronous pumping at 100 MHz yielded 7.7 ps pulses with 15 mW average power. These were shortened to 1. 1 ps pulses with 64 W peak power by chirp compensation using diffraction gratings, and to 710 fs by negative group‐velocity dispersion in an optical fiber.

Sub‐100 femtosecond pulses from an external‐cavity surface‐emitting InGaAs/InP multiple quantum well laser with soliton‐effect compression

We have compressed strongly chirped optical pulses from a synchronously pumped In0.53Ga0.47As/InP multiple quantum well surface‐emitting laser operating with an external cavity. The pulses, initially exhibiting a strong up‐chirp with a time‐bandwidth product of more than 100 times the Fourier transform limit, were compressed to 77 fs using dispersion and soliton compression in a negative group‐velocity‐dispersion fiber. Chirp compensation using a diffraction grating pair followed by soliton compression in a fiber gave pulses as short as 21 fs.

Femtosecond external-cavity surface-emitting InGaAs/InP multiple-quantum-well laser

We demonstrate that a synchronously pumped In0.53Ga0.47As/InP multiple-quantum-well surface-emitting laser in an external cavity can produce 36-ps pulses with a high average power of 260 mW and a broad spectral width of 18 nm. The output pulses are strongly upchirped and could be shortened to 153 fs with peak powers exceeding 1 kW by chirp compensation with a diffraction grating pair.

Soliton fusion and steering by the simultaneous launch of two different-color solitons.

Two optical solitons with different center frequencies simultaneously launched into an optical fiber are considered. By numerical simulation and by experiment, it is shown that if their frequency separation is small, they will either merge into a single pulse (fusion) or form two pulses with different velocities (steering), depending on their phase difference. With a 400-m fiber and ~2.5-ps solitons at 1457.7 and 1460.7 nm, fusion and steering of as much as 7 ps are demonstrated.

Breakup of bound higher-order solitons

Bound higher-order solitons, sometimes called breather solitons, can easily be broken apart by small perturbations. We discuss the conditions for breakup of bound solitons and describe a method to determine the details of the soliton breakup. Using this method, we illustrate the breakup of bound solitons by optical filters, by asymmetric FM modulation (not AM or symmetric FM modulation), and by superposition with other optical pulses.

Soliton-collision interferometer for the quantum nondemolition measurement of photon number: numerical results

Using analytic theory and numerical experiments, we show that a quantum nondemolition measurement of the photon number of optical solitons in a single-mode optical fiber can be made. We describe the soliton-collision interferometer with which we propose to make this measurement and discuss simulations of the performance of this interferometer.

High power and high efficiency vertical cavity surface emitting GaAs laser

We report high power and high efficiency operation of a vertical cavity surface emitting GaAs laser in an external cavity. The maximum cw output power from the fundamental TEM00 mode was 700 mW at a temperature of 77 K when pumped by a cw krypton‐ion laser with 1.8 W pump power. We obtained an absolute quantum efficiency (pump photons to lasing photons) of 44%, and a differential efficiency above threshold of 58%.

Ultrafast optical pulse noise suppression using a nonlinear spectral filter: 23 dB reduction of fiber laser 1/f noise

Nonlinear spectral filtering provides a simple method for reducing noise in optical pulses to below the shot noise level. We show its effectiveness for excess noise reduction in an ultrafast optical pulse train by demonstrating 23 dB reduction of low frequency 1/f noise in pulses from a passively mode-locked erbium-doped fiber laser. The noise reduction is achieved by spectrally filtering pulses propagated as solitons through a 1.5 km length of optical fiber.

Solitons for optical time-domain reflectometry

We describe the propagation of solitons in an optical time-domain reflectometry geometry. Intense nonsolitons usually broaden nonlinearly as they propagate out to a scatterer and broaden linearly as they return to their origin. In contrast, solitons propagate with a fixed pulse width or narrow on their way out to the scatterer. Returning, they broaden or narrow depending on their chirp at the scattering point. For a fixed return-pulse timing resolution we find 2.6 times or more energy can be launched when solitons are used than for normal dispersion pulses.

Direct observation of soliton and normal pulse propagation by spectral domain reflectometry.

We report what are to our knowledge the first continuous observations of optical fiber solitons and nonsoliton pulses in the spectral domain. Using a novel optical time-resolved spectral ref lectometer that measures the backscattered light spectrum, we directly observed (with 200-m spatial resolution) the propagation of ~8.5-ps solitons and nonsolitons traveling down 5-km fibers. Spectral breathing and the recovery of the original spectral widths are clearly seen for higher-order solitons. Possible applications include in situ measurements of soliton parameters, fiber dispersions, and nonlinearities, experimental verifications of pulse propagation theories, and optical sensing.