On a class of bimodal oscillations powered by a steady, zero-frequency force-Implications to energy conversion and structural stability.

I propose that there exists in natural and artificial environments a class of resonant oscillations that can be excited directly by a steady, zero-frequency force such as that of wind, water, electric field. A member of this class comprises two normally independent oscillating modes of a system, for example, a building or bridge, which, separately, cannot be driven by a zero-frequency force. Agreeing on terms of collaboration, the two modes engage in a joint oscillation powered by the steady zero-frequency force in which they drive each other, one directly and the other parametrically.

Consequences of quantum noise control for the relaxation resonance frequency and phase noise in heterogeneous Silicon/III-V lasers.

We have recently introduced a new semiconductor laser design which is based on an extreme, 99%, reduction of the laser mode absorption losses. In previous reports, we showed that this was achieved by a laser mode design which confines the great majority of the modal energy (> 99%) in a low-loss Silicon guiding layer rather than in highly-doped, thus lossy, III-V p[Formula: see text] and n[Formula: see text] layers, which is the case with traditional III-V lasers. The resulting reduced electron-field interaction was shown to lead to a commensurate reduction of the spontaneous emission rate by the excited conduction band electrons into the laser mode and thus to a reduction of the frequency noise spectral density of the laser field often characterized by the Schawlow-Townes linewidth.

Quantum Wave-Particle Duality in Free-Electron-Bound-Electron Interaction.

We present a comprehensive relativistic quantum-mechanical theory for interaction of a free electron with a bound electron in a model, where the free electron is represented as a finite-size quantum electron wave packet (QEW) and the bound electron is modeled by a quantum two-level system (TLS). The analysis reveals the wave-particle duality nature of the QEW, delineating the point-particle-like and wavelike interaction regimes and manifesting the physical reality of the wave function dimensions when interacting with matter. This QEW size dependence may be used for interrogation and coherent control of superposition states in a TLS and for enhancement of cathodoluminescence and electron energy-loss spectroscopy in electron microscopy.

Kicking the habit/semiconductor lasers without isolators.

In this paper, we propose and demonstrate a solution to the problem of coherence degradation and collapse caused by the back reflection of laser power into the laser resonator. The problem is most onerous in semiconductor lasers (SCLs), which are normally coupled to optical fibers, and results in the fact that practically every commercial SCL has appended to it a Faraday-effect isolator that blocks most of the reflected optical power preventing it from entering the laser resonator. The isolator assembly is many times greater in volume and cost than the SCL itself.

Higher-order QAM data transmission using a high-coherence hybrid Si/III-V semiconductor laser.

We experimentally demonstrate the use of a high-coherence hybrid silicon (Si)/III-V semiconductor laser as the light source for a transmitter generating 20 Gbaud 16- and 64- quadrature amplitude modulated (QAM) data signals over an 80 km single-mode fiber (SMF) link. The hybrid Si/III-V laser has a measured Schawlow-Townes linewidth of ${\sim}{10}\;{\rm kHz}$∼10kHz, which is achieved by storing modal optical energy in low-loss Si, rather than the relatively lossy III-V materials. We measure a received bit error rate (BER) of ${4.

Free-Electron-Bound-Electron Resonant Interaction.

Here we present a new paradigm of free-electron-bound-electron resonant interaction. This concept is based on a recent demonstration of the optical frequency modulation of the free-electron quantum electron wave function (QEW) by an ultrafast laser beam. We assert that pulses of such QEWs correlated in their modulation phase, interact resonantly with two-level systems, inducing resonant quantum transitions when the transition energy ΔE=ℏω_{21} matches a harmonic of the modulation frequency ω_{21}=nω_{b}.

Vernier spectrometer using counterpropagating soliton microcombs.

Determination of laser frequency with high resolution under continuous and abrupt tuning conditions is important for sensing, spectroscopy, and communications. We show that a single microresonator provides rapid and broadband measurement of optical frequencies with a relative frequency precision comparable to that of conventional dual-frequency comb systems. Dual-locked counterpropagating solitons having slightly different repetition rates were used to implement a vernier spectrometer, which enabled characterization of laser tuning rates as high as 10 terahertz per second, broadly step-tuned lasers, multiline laser spectra, and molecular absorption lines.

Quantum control of phase fluctuations in semiconductor lasers.

Few laser systems allow access to the light-emitter interaction as versatile and direct as that afforded by semiconductor lasers. Such a level of access can be exploited for the control of the coherence and dynamic properties of the laser. Here, we demonstrate, theoretically and experimentally, the reduction of the quantum phase noise of a semiconductor laser through the direct control of the spontaneous emission into the laser mode, exercised via the precise and deterministic manipulation of the optical mode's spatial field distribution.

1.6 kW Yb fiber amplifier using chirped seed amplification for stimulated Brillouin scattering suppression.

In a high power fiber amplifier, a frequency-chirped seed interrupts the coherent interaction between the laser and Stokes waves, raising the threshold for stimulated Brillouin scattering (SBS). Moving the external mirror of a vertical cavity surface-emitting diode laser 0.2 μm in 10 μs can yield a frequency chirp of 5×10  Hz/s at a nearly constant output power.

On-chip integrated differential optical microring refractive index sensing platform based on a laminar flow scheme.

We propose an on-chip integrated differential optical microring refractive index sensing platform which leverages laminar flow conditions. Close spacing between a sensing and a reference resonator, and sharing the same microfluidic channel allows the two resonators to experience similar environmental disturbances, such as temperature fluctuations and fluidic-induced transients, achieving reliable and sensitive sensing performance. We obtain a noise floor of 80.

High-coherence semiconductor lasers based on integral high-Q resonators in hybrid Si/III-V platforms.

The semiconductor laser (SCL) is the principal light source powering the worldwide optical fiber network. The ever-increasing demand for data is causing the network to migrate to phase-coherent modulation formats, which place strict requirements on the temporal coherence of the light source that no longer can be met by current SCLs. This failure can be traced directly to the canonical laser design, in which photons are both generated and stored in the same, optically lossy, III-V material.

Phase-locking and coherent power combining of broadband linearly chirped optical waves.

We propose, analyze and demonstrate the optoelectronic phase-locking of optical waves whose frequencies are chirped continuously and rapidly with time. The optical waves are derived from a common optoelectronic swept-frequency laser based on a semiconductor laser in a negative feedback loop, with a precisely linear frequency chirp of 400 GHz in 2 ms. In contrast to monochromatic waves, a differential delay between two linearly chirped optical waves results in a mutual frequency difference, and an acoustooptic frequency shifter is therefore used to phase-lock the two waves.

"Ideal" optical delay lines based on tailored-coupling and reflecting, coupled-resonator optical waveguides.

We present a design of "ideal" optical delay lines (i.e., constant amplitude and constant group delay over the desired bandwidth).

Designing coupled-resonator optical waveguides based on high-Q tapered grating-defect resonators.

We present a systematic design of coupled-resonator optical waveguides (CROWs) based on high-Q tapered grating-defect resonators. The formalism is based on coupled-mode theory where forward and backward waveguide modes are coupled by the grating. Although applied to strong gratings (periodic air holes in single-mode silicon-on-insulator waveguides), coupled-mode theory is shown to be valid, since the spatial Fourier transform of the resonant mode is engineered to minimize the coupling to radiation modes and thus the propagation loss.

Synthesis of high-order bandpass filters based on coupled-resonator optical waveguides (CROWs).

We present a filter design formalism for the synthesis of coupled-resonator optical waveguide (CROW) filters. This formalism leads to expressions and a methodology for deriving the coupling coefficients of CROWs for the desired filter responses and is based on coupled-mode theory as well as the recursive properties of the coupling matrix. The coupling coefficients are universal and can be applied to various types of resonators.

Multiple source frequency-modulated continuous-wave optical reflectometry: theory and experiment.

We propose and demonstrate a novel approach to increase the effective bandwidth of a frequency-modulated continuous-wave (FMCW) ranging system. This is achieved by algorithmically stitching together the swept spectra of separate laser sources. The result is an improvement in the range resolution proportional to the increase in the swept-frequency range.

Sideband locking of a single-section semiconductor distributed-feedback laser in an optical phase-lock loop.

The bandwidth and performance of optical phase-lock loops (OPLLs) using single-section semiconductor lasers (SCLs) are severely limited by the nonuniform frequency modulation response of the lasers. It is demonstrated that this restriction is eliminated by the sideband locking of a single-section distributed-feedback SCL to a master laser in a heterodyne OPLL, thus enabling a delay-limited loop bandwidth. The lineshape of the phase-locked SCL output is characterized using a delayed self-heterodyne measurement.

Precise control of broadband frequency chirps using optoelectronic feedback.

We demonstrate the generation of wideband frequency sweeps using a semiconductor laser in an optoelectronic feedback loop. The rate and shape of the optical frequency sweep is locked to and determined by the frequency of a reference electronic signal, leading to an agile, high coherence swept-frequency source for laser ranging and 3-D imaging applications. Using a reference signal of constant frequency, a transform-limited linear sweep of 100 GHz in 1 ms is achieved, and real-time ranging with a spatial resolution of 1.

An exact transverse Helmholtz equation.

We derive an exact equation for the transverse component of the electric field propagating along a given longitudinal z direction in the presence of an isotropic refractive-index distribution n(x,y).

Grating induced transparency (GIT) and the dark mode in optical waveguides.

We propose and describe a new class of optical modes consisting of superposition of three waveguide modes which can be supported by a few-mode waveguide spatially modulated by two co-spatial gratings. These supermodes bear a close, but not exact, formal analogy to the three-level quantum states involved in EIT and its attendant slow light propagation characteristics. Of particular interest is the supermode which we call the dark mode in which, in analogy with the dark state of EIT, one of the three uncoupled waveguide modes is not excited.

Surface-emitting circular DFB, disk-, and ring-Bragg resonator lasers with chirped gratings. III: gain saturation effects and above-threshold analysis.

As Part III of this series, this paper focuses on an above-threshold modal analysis which includes gain saturation effects in the surface-emitting chirped circular grating lasers. We derive an exact energy relation which states that, in steady state, the net power generated in the gain medium is equal to the sum of peripheral leakage power and vertical emission power. This relation is particularly useful in checking the accuracy of numerical mode solving.

Electrically pumped hybrid evanescent Si/InGaAsP lasers.

Hybrid Si/III-V, Fabry-Perot evanescent lasers are demonstrated, utilizing InGaAsP as the III-V gain material for the first time to our knowledge. The lasing threshold current of 300-mum-long devices was as low as 24 mA, with a maximal single facet output power of 4.2 mW at 15 degrees C.

Adiabaticity criterion and the shortest adiabatic mode transformer in a coupled-waveguide system.

By analyzing the propagating behavior of the supermodes in a coupled-waveguide system, we have derived a universal criterion for designing adiabatic mode transformers. The criterion relates epsilon, the fraction of power scattered into the unwanted mode, to waveguide design parameters and gives the shortest possible length of an adiabatic mode transformer, which is approximately 2/piepsilon1/2 times the distance of maximal power transfer between the waveguides. The results from numerical calculations based on a transfer-matrix formalism support this theory very well.

Surface-emitting circular DFB, disk-, and ring-Bragg resonator lasers with chirped gratings. II: nonuniform pumping and far-field patterns.

This is a continuation of our previous work [Opt. Express 16, 9155 (2008)]. In this paper we investigate the effect of nonuniform pumping on the modal properties of surface-emitting chirped circular grating lasers.