Corrections to the rate equation approximation for dynamic considerations in a semiconductor laser

Corrections to the rate equation approximation are derived and applied to a semiconductor laser. Whereas these corrections do not affect the operating point of the device, they do alter the dynamic operation. To first order the correction produces a renormalization of familiar dynamic parameters. This renormalization, in turn, leads to a 20% correction to the field spectrum linewidth formula

Quantum box fabrication tolerance and size limits in semiconductors and their effect on optical gain

Lower and upper limits on size are established for quantum boxes. The lower limit is shown to result from a critical size below which bound electronic states no longer exist. This critical size is different for electrons and holes. The optical gain of arrays of quantum boxes is computed taking into account the inhomogenous broadening of the gain spectrum resulting from fabricational variations in quantum box size and shape. The dependence of maximum possible gain on an rms quantum box roughness amplitude is determined. For high gain operation a medium composed of quantum boxes does not offer significant advantages over a conventional bulk semiconductor unless quantum box fabricational tolerances are tightly controlled. For low gain operation, however, arrays of quantum boxes may offer the unique advantage of optical transparency at zero excitation. This property does not require excellent fabricational control and may make possible ultralow threshold semiconductor lasers and low noise optical amplifiers

Highly efficient hybrid fiber taper coupled microsphere laser

A novel hybrid fiber taper is proposed and demonstrated as the coupler in a microsphere laser system. The pump wave and the laser emission, respectively, are more efficiently coupled to and from the sphere modes with this taper structure. A 980-nm pumped erbium–ytterbium codoped phosphate microsphere laser is demonstrated in the 1550-nm band. As much as 112 µW of single-frequency laser output power was measured, with a differential quantum efficiency of 12%

Detuned loading in coupled cavity semiconductor lasers — effect on quantum noise and dynamics

We derive the modulation and noise properties of a semiconductor laser consisting of an active cavity loaded by a passive cavity. The results indicate that under certain conditions the direct modulation bandwidth can be doubled with simultaneous phase noise reduction as compared to a conventional laser

Highly efficient optical power transfer to whispering-gallery modes by use of a symmetrical dual-coupling configuration

We report that greater than 99.8% optical power transfer to whispering-gallery modes was achieved in fused-silica microspheres by use of a dual-tapered-fiber coupling method. The intrinsic cavity loss and the taper-to-sphere coupling coefficient are inferred from the experimental data. It is shown that the low intrinsic cavity loss and the symmetrical dual-coupling structure are crucial for obtaining the high coupling efficiency

Semiclassical Theory of Noise in Semiconductor Lasers-Part I

A Van der Pol analysis of laser noise which includes the field intensity dependence of the refractive index is presented. The consequent amplitude phase coupling affects all laser spectra except the power fluctuations spectrum. An analytic expression for the linewidth broadening enhancement due to index variation is given

Occupation fluctuation noise: A fundamental source of linewidth broadening in semiconductor lasers

In this letter we consider the effect of fast thermal fluctuations of electronic state occupancy on the field spectrum of semiconductor lasers and derive for the first time an expression for the resulting power independent linewidth contribution. The magnitude and temperature dependence of this linewidth component agree reasonably well with measurements of a power independent linewidth made by Welford and Mooradian

Observation of Kerr nonlinearity in microcavities at room temperature

We have devised and experimentally verified a method for observation of the optical Kerr effect in microcavities at room temperature. The technique discriminates against the much larger and typically dominant thermal component of nonlinearity by using its relatively slow frequency response. Measurement of the Kerr coefficient or equivalently of the third-order nonlinear susceptibility of the cavity material is demonstrated for a silica microcavity. With this approach, useful information about the characteristic thermal response time in microresonators can also be acquired

Highly nondegenerate four-wave mixing efficiency of an asymmetric coupled quantum well structure

An asymmetric coupled quantum well structure is theoretically investigated as a means of tailoring the conversion efficiency of the four-wave mixing process at terahertz detuning rates. In this structure, a coherent electronic oscillation between the two wells can be excited that introduces a resonance peak in the four-wave mixing frequency response. A calculation based on the density matrix formalism shows that an increase in the power conversion efficiency on the order of 10 dB can be attained at the selected resonance frequency for low temperature operation. Finally, we propose a novel technique for exciting the interwell oscillations that takes advantage of the polarization dependence of the interband optical transitions in alternating strain quantum wells

Soliton Microcomb Range Measurement

Laser-based range measurement systems (LIDAR) are important in many application areas including autonomous vehicles, robotics, manufacturing, formation-flying of satellites, and basic science. Coherent laser ranging systems using dual frequency combs provide an unprecedented combination of long range, high precision and fast update rate. Here, dual-comb distance measurement using chip-based soliton microcombs is demonstrated. Moreover, the dual frequency combs are generated within a single microresonator as counter-propating solitons using a single pump laser. Time-of-flight measurement with 200 nm precision at 500 ms averaging time is demonstrated. Also, the dual comb method extends the ambiguity distance to 26 km despite a soliton spatial period of only 16 mm. This chip-based source is an important step towards miniature dual-comb laser ranging systems that are suitable for photonic integration