Photonic crystal resonators for inverse-designed multi-dimensional optical interconnects.

We experimentally demonstrate a 400 Gbit/s optical communication link utilizing wavelength-division multiplexing and mode-division multiplexing for a total of 40 channels. This link utilizes a novel, to the best of our knowledge, 400 GHz frequency comb source based on a chip-scale photonic crystal resonator. Silicon-on-insulator photonic inverse-designed 4 × 4 mode-division multiplexer structures enable a fourfold increase in data capacity. We show less than -10 dBm of optical receiver power for error-free data transmission in 34 out of a total of 40 channels using a PRBS31 pattern.

Measurement of carrier envelope offset frequency for a 10 GHz etalon-stabilized semiconductor optical frequency comb.

We report Carrier Envelope Offset (CEO) frequency measurements of a 10 GHz harmonically mode-locked, Fabry-Perot etalon-stabilized, semiconductor optical frequency comb source. A modified multi-heterodyne mixing technique with a reference frequency comb was utilized for the measurement. Also, preliminary results from an attempt at f-2f self-referencing measurement are presented. The CEO frequency was found to be ~1.47 GHz for the particular etalon that was used.

Dynamic line-by-line pulse shaping with GHz update rate.

We introduce a novel scheme for dynamic line-by-line pulse shaping with GHz update rates. Four lines of an optical frequency comb source are used to injection-lock four individual VCSEL, which are subsequently electrically modulated at 0.4 to 1 GHz through current modulation. This concept could be considered a completely new way of pulse shaping as the light is not simply modified, but rather regenerated with the desired properties. We also discuss an important drawback of line-by-line pulse shapers that ultimately limits the modulation speed capability.

Intracavity dispersion effect on timing jitter of ultralow noise mode-locked semiconductor based external-cavity laser.

We report the generation of optical pulse trains with 380 as of residual timing jitter (1 Hz-1 MHz) from a mode-locked external-cavity semiconductor laser, through a combination of optimizing the intracavity dispersion and utilizing a high-power, low-noise InGaAsP quantum-well slab-coupled optical waveguide amplifier gain medium. This is, to our knowledge, the lowest residual timing jitter reported to date from an actively mode-locked laser.

Ultralow-noise mode-locked optical pulse trains from an external cavity laser based on a slab coupled optical waveguide amplifier (SCOWA).

We report the generation of optical pulse trains with 8.5 fs timing jitter (10 Hz to 10 MHz) from a mode-locked semiconductor laser, with a slab coupled optical waveguide amplifier used as the gain element. This is, to our knowledge, the lowest residual timing jitter reported to date from an actively mode-locked laser.

Supermode suppression to below -130 dBc/Hz in a 10 GHz harmonically mode-locked external sigma cavity semiconductor laser.

We demonstrate supermode suppression to levels below -125 dBc/Hz and -132 dBc/Hz using Fabry-Perot etalons with finesse values of 180 and 650, respectively, for a 10 GHz harmonically mode-locked external sigma cavity semiconductor laser. The laser was hybridly mode-locked using direct electrical modulation in a compact package without the need for an external modulator.

Ultralow noise and supermode suppression in an actively mode-locked external-cavity semiconductor diode ring laser.

We report what is to our knowledge the lowest phase and amplitude noise characteristics achieved to date in a 10-GHz pulse train produced by the active harmonic mode locking of an external-cavity semiconductor diode laser. Supermode noise has also been suppressed below -140 dBc/Hz by use of a high-finesse fiber Fabry-Perot etalon as an intracavity filter. Novel noise sideband measurements that extend to the Nyquist offset frequency suggest a significant advantage in using harmonic (rather than fundamental) mode locking to produce ultralow-noise pulse trains, owing to the relationship between the noise roll-off frequency and the fundamental cavity frequency.

Measurement of residual phase noise and longitudinal-mode linewidth in a hybridly mode-locked external linear cavity semiconductor laser.

We report measurements of the residual phase-noise knee position and longitudinal-mode linewidth of a hybridly mode-locked external linear cavity semiconductor laser as a function of laser cavity length. Excellent agreement between these measurements suggests a direct relationship between rms pulse-to-pulse timing jitter and average longitudinal-mode linewidth. This relationship leads to a fundamental limit in the timing jitter of mode-locked lasers.

Hybrid wavelength-division and optical time-division multiplexed multiwavelength mode-locked semiconductor laser.

A multiwavelength laser source composed of a single semiconductor optical amplifier and a commercially available off-the-shelf wavelength-division multiplexed (WDM) filter is constructed and tested under actively mode-locking operation. Five independent mode-locked wavelength channels are generated simultaneously, with a wavelength spacing of 1.6 nm established by the WDM filter. In addition, to demonstrate the potential of this mixed time-frequency, or hybrid WDM-optical time-division multiplexed, signal, we demonstrate a simple parallel-to-serial wavelength conversion to increase the pulse repetition rate of the mode-locked laser by a number of output wavelengths for applications in high-performance optical sampling applications.

Demonstration of phase correlation in multiwavelength mode-locked semiconductor diode lasers.

Wideband spectral phase correlation is demonstrated from a multiwavelength mode-locked semiconductor laser. By use of frequency-resolved optical gating techniques, significant phase correlation was observed between multiple intracavity oscillating wavelengths, with wavelength separations of ~1 nm . The resultant temporal characteristics show a substantial modulation owing to the spectral coupling induced by intracavity-generated four-wave mixing. This result may lead to novel methods for directly generating ultrafast subpicosecond optical pulse sequences with spectrally tailored amplitude and phase characteristics from actively mode-locked semiconductor lasers.

Ultrafast semiconductor laser-diode-seeded Cr:LiSAF regenerative amplifier system.

An ultrafast, hybrid mode-locked semiconductor laser-diode system has been used to seed a flash-lamp-pumped Cr:LiSAF regenerative amplifier system, producing subpicosecond pulses with millijoule output pulse energy. This system has the potential to eliminate argon-ion-pumped-based, ultrafast laser systems.

Generation of pulses as short as 93 fs from self-starting femtosecond Cr:LiSrAlF(6) lasers by exploiting multiple-quantum-well absorbers.

A Cr:LiSrAIF(6) laser has been mode locked by using a multiple-quantum-well (MQW) absorber. With the MQW absorber inside the laser cavity, Kerr lens mode locking is initiated, yielding transform-limited pulses as short as 93 fs. Pulses of 500-fs duration have also been produced by using resonant passive mode locking with the MQW absorber in an external cavity.

Mode-locked all-solid-state diode-pumped Cr:LiSAF laser.

A diode-pumped mode-locked Cr:LiSAF laser is demonstrated for what is to our knowledge the first time. Active mode locking, with an acousto-optic modulator, and resonant passive mode locking, with a multiple-quantum-well absorber in an external cavity, have both yielded cw trains of picosecond pulses.

200-fs optical pulse generation and intracavity pulse evolution in a hybrid mode-locked semiconductor diode-laser/amplifier system.

Optical pulses of 200 fs with 165 W of peak power have been generated from an AlGaAs semiconductor diode-laser system. These pulses represent, to our knowledge, both the shortest and most intense ever generated from an all-semiconductor injection diode-laser system. The intracavity pulse evolution in the external cavity is also investigated experimentally. The findings show that the large nonlinearities associated with gain depletion and saturable absorption cause appreciable spectral and temporal modification of the mode-locked optical pulse as it oscillates in the laser cavity.

Generation of subpicosecond high-power optical pulses from a hybrid mode-locked semiconductor laser.

Ultrashort optical pulses 0.46 psec in duration with over 70 W of peak power are generated from an all-semiconductor laser-diode system. These results represent to our knowledge both the shortest and most-intense optical pulses generated from an all-semiconductor laser system.

Real-time measurements of phonon lifetime using a streak-camera-Raman-induced phase-conjugation method.

A novel real-time technique to measure phonon dynamics using the Raman-induced phase-conjugation method in combination with streak-camera technology is described. The technique is used to determine vibrational and optical phonon dephasing kinetics of CS(2), calcite, and LiNbO(3) with a temporal resolution of 3 psec.

Picosecond Raman-induced phase conjugation in liquids and solids.

We have used the new Raman-induced phase conjugate (RIPC) technique to obtain strong Raman signals using picosecond laser pulses. We have obtained the picosecond RIPC spectra of carbon disulfide, benzene, nitrobenzene, and calcite. By delaying one of the interacting pump beams relative to the other pump and probe beams we were able to determine the intensities of the phase conjugate beams at the Stokes frequencies as a function of time with 20-ps resolution. These measurements show the potential of this technique to determine phonon relaxation times in condensed matter using shorter laser pulses.