Coherent Semiconductor Laser Research Articles

General recipe to realize photonic-crystal surface-emitting lasers with 100-W-to-1-kW single-mode operation

Realization of one-chip, ultra-large-area, coherent semiconductor lasers has been one of the ultimate goals of laser physics and photonics for decades. Surface-emitting lasers with two-dimensional photonic crystal resonators, referred to as photonic-crystal surface-emitting lasers (PCSELs), are expected to show promise for this purpose. However, neither the general conditions nor the concrete photonic crystal structures to realize 100-W-to-1-kW-class single-mode operation in PCSELs have yet to be clarified. Here, we analytically derive the general conditions for ultra-large-area (3~10 mm) single-mode operation in PCSELs. By considering not only the Hermitian but also the non-Hermitian optical couplings inside PCSELs, we mathematically derive the complex eigenfrequencies of the four photonic bands around the Γ point as well as the radiation constant difference between the fundamental and higher-order modes in a finite-size device. We then reveal concrete photonic crystal structures which allow the control of both Hermitian and non-Hermitian coupling coefficients to achieve 100-W-to-1-kW-class single-mode lasing.

Novel high-power and coherent semiconductor laser with a shaped unstable resonator

We describe a novel high power semiconductor laser that employs a shaped unstable resonator waveguide to maintain fundamental spatial mode operation at high power levels. We call this device the SHUR (shaped unstable resonator) laser. By photoetching and regrowth we locate a secondary, nonplanar antiguide, beneath the main part of the waveguide. The lasing mode couples to this secondary guide and experiences lateral antiguiding, which is the basis of the unstable resonator action. Prototype versions of the SHUR laser show a maximum pulsed output power of 770 mW per facet. The focused beam is dominated by a single lobe that contains 47% of the output power.

Spatiospectral and picosecond spatiotemporal properties of a broad area operating channeled-substrate-planar laser array

Spatiospectral and spatiotemporal properties of an eight-element channeled-substrate-planar laser array are investigated in both cw and pulsed operating conditions. The closely spaced CSP array with strong optical coupling between array elements is characterized by a broad area laserlike operation determined by its spatial mode spectra. The spatiotemporal evolution of the near and far field exhibits complex dynamic behavior in the picosecond to nanosecond domain. Operating parameters for the laser device have been experimentally determined. These results provide important information for the evaluation of the dynamic behavior of coherent semiconductor laser arrays.

FM characteristics and compact modules for coherent semiconductor lasers coupled to an external cavity

Measured FM responses of a semiconductor laser optically coupled off-axis to a confocal Fabry-Perot cavity are discussed. It was found that this cavity acted as a frequency discriminator and as a phase comparator for slow and fast frequency fluctuations, respectively. The crossover between them was determined by a half linewidth of the cavity. On the basis of these investigations, two kinds of coherent semiconductor laser modules were constructed. External Fabry-Perot cavities were made by using an optical fiber and a hemispherical microlens. The linewidths of these lasers were less than 25 kHz. >

Surface-emitting two-dimensional coherent semiconductor laser array

We describe a new surface-emitting semiconductor structure, its fabrication, and its performance. Phase-locked emission takes place from a region much larger than the wavelength in two dimensions; therefore we term this device a two-dimensional coherent array. The key feature of our device is that the radiation is coupled directly from the active region using a nonresonant grating coupler, i.e., the grating is of noninteger order.

Analysis and observation of coupling ratio dependence of Rayleigh backscattering noise in a fiber optic gyroscope

Noise due to Rayleigh backscattering in a fiber-optic gyroscope is observed in quadrature with the Sagnac signal. This noise can be nulled by adjustment of the coupling ratio of the loop coupler and the state of polarization in the gyro loop. A rigorous analysis of the phases of, and the modulations applied to, the primary and scattered beams shows that no coherent Rayleigh backscatter noise should be detected on the Sagnac signal even with relatively coherent semiconductor laser sources. >

The Clifford Parterson Lecture, 1983 Optical fibre communication, present and future

The original objectives established in the mid-1960s for optical fibre systems were more than met by the first production equipment in1980. Now, second-generation single-mode systems, with still greater per­formance, are entering service. However, current research shows that the technology is still in its infancy. The use of highly coherent semiconductor laser transmitters coupled with heterodyne detection has given large improvements in receiver sensitivity. Understanding the nonlinear properties of glass fibres has paved the way to higher transmitter powers and the use of picosecond pulses. Many integrated-optic components such as modulators, couplers and other components will probably be used while the monolithic integration of optical and electronic components may lead to further cost reductions. The paper will describe these advances, examine their possible appli­cations in systems and discuss how these may be exploited in the future.

Reduction of optical phase noise in semiconductor lasers

There are several applications of highly coherent semiconductor lasers, especially in coherent optical-fibre communications systems and optical-fibre sensors. Optical phase noise is extremely important in these applications. Here we report preliminary results from a simple technique whereby phase noise in semiconductor lasers may be reduced. Initial results demonstrate a phase-noise reduction of typically 20 dB. Developments of the technique should permit reduction towards the shot noise limit.