Influence Of Spatial Hole Burning Research Articles

Design and analysis of large-area vertical-cavity semiconductor optical amplifiers with anti-resonant reflecting optical waveguide

The optical characteristics of antiresonant reflecting optical waveguide (ARROW) vertical-cavity semiconductor optical amplifiers (VCSOAs) are investigated theoretically. Influence of spatial hole burning (SHB) and thermal lensing on the stability of the amplified output signal is taken into consideration in the studies. A design rule, which can be used to deduce the optimized dimensions of ARROW, is developed to achieve spatially stable single-spot amplified output-signal in large-area VCSOAs. It can be shown that a high saturation power yet stable output signal can be achieved in large-area ARROW VCSOAs simultaneously.

Transverse-Leaky-Mode Characteristics of ARROW VCSELs

Transverse-leaky-mode characteristics of antiresonant-reflecting-optical-waveguide (ARROW) vertical-cavity surface-emitting lasers (VCSELs) are studied. It is found that the suppression of high-order transverse leaky modes in ARROW VCSELs can be deteriorated by the influence of spatial hole burning and thermal lensing effects. On the other hand, a new design rule is proposed to deduce the optimum dimensions of ARROW so that the suppression of high-order transverse leaky modes can be enhanced. Furthermore, the turn-on transient response of ARROW VCSELs is investigated. It is found that the radiation loss has significant influence on the built-up time of the first-order transverse leaky mode.

Polarization selection in birefringent antiresonant reflecting optical waveguide-type vertical-cavity surface-emitting lasers

The influence of spatial hole burning and thermal lensing effects on the polarization selection mechanism of the birefringent antiresonant reflecting optical waveguide (ARROW) type vertical-cavity surface-emitting lasers (VCSELs) is studied. Competition between the two orthogonal polarizations with a similar fundamental lateral-mode profile, arising from refractive index anisotropies inside the laser cavities, is considered in the analysis. It can be shown that the single-mode operation of ARROW VCSELs is more stable than that of simplified-ARROW VCSELs provided that strong confinement of injection current as well as minimization of thermal lensing effects can be realized. In addition, a small refractive index difference is adequate to ensure stable single-mode operation in ARROW VCSELs.

High-power single-mode operation in DFB and FP lasers using diffused quantum-well structure

Distributed feedback (DFB) and Fabry-Perot (FP) semiconductor lasers with step and periodic interdiffusion quantum-well structures are proposed for high-power single-longitudinal-mode operation. It is shown that the phase-adjustment region formed by the diffusion step (i.e., step change in optical gain and refractive index) counteracts the influence of spatial hole burning, especially for DFB lasers with large coupling-length products biased at high injection current. Furthermore, it is found that with careful design of the diffusion grating (i.e., grating period and amount of diffusion extent) of FP lasers, side-mode suppression ratio can be enhanced and threshold current density can be minimized to a satisfied level.

Semiclassical model of semiconductor laser noise and amplitude noise squeezing. II. Application to complex laser structures

For pt.I see ibid., vol.33, no.11, p.2097-2104 (1997). We present noise studies of distributed feedback (DFB) laser structures, where spatial hole burning (SHB) plays a key role performed using the model described in part I of this paper with particular emphasis on the influence of SHB, on the coupling coefficient /spl kappa/L, and on the laser facet reflectivities. These structures exhibit high amplitude noise and the possible noise reduction is strongly reduced compared to Fabry-Perot structures. Distributed Bragg reflector (DBR) lasers are better candidates even if their performances are also strictly determined by SHB and the loss in the Bragg reflector. Finally, limitations due to gain suppression are demonstrated for such complex lasers structures. We conclude on the optimum laser structure for amplitude squeezed states generation.

An accurate rate-equation description for DFB lasers and some interesting solutions

Starting from the coupled-wave equations, we have derived an alternative set of rate equations which are valid for most single-section distributed feedback (DFB) lasers. These rate equations are in many respects more useful than the conventional rate equations and have also been used to derive the influence of spatial hole burning on characteristics such as the chirp, the linewidth, or the harmonic distortion. Numerical results are presented for a DFB laser with both facets cleaved, AR-coated, and for a /spl lambda//4-shifted DFB laser.

Influence of spatial hole burning effects on relaxation oscillations in waveguide distributed feedback Nd 3+:YAG lasers

The influence of spatial hole burning on the relaxation oscillations is discussed in planar and fiber distributed feedback lasers without and with end reflectivity. In our analysis the threshold field approximation is used in coupled rate equations. The laser characteristics are obtained as a function of the system parameters for Nd 3+:YAG waveguide lasers. It is shown that in general the spatial hole burning effect increases the damping rate and the frequency of the relaxation oscillations. Moreover, this effect affects laser characteristics stronger in the fiber structure.

Influence of the axially varying quasi-Fermi-level separation of the active region on spatial hole burning in distributed-feedback semiconductor lasers

The longitudinal-mode characteristics of distributed-feedback semiconductor lasers subjected to longitudinal spatial hole burning have been investigated using an improved numerical modeling scheme. The main new feature of the model is that it allows for the natural axial variations of the separation between the quasi-Fermi levels (Fermi voltage) in the laser’s active region. This gives rise to a current density injected into the active region that varies along the laser axis, even for uniformly biased lasers. It is found that compared to the results obtained by assuming an uniform current density, the detrimental influence of the longitudinal spatial hole burning on important static characteristics of quarter-wave-shifted distributed-feedback lasers, such as the gain margin and the lasing wavelength stability, is weakened. Therefore, the usual assumption of an uniform injected current density gives rise to an overestimated influence of the spatial hole burning, this overestimation being more important for long-cavity lasers having a grating structure with a large coupling coefficient.

Theoretical investigation of the second-order harmonic distortion in the AM response of 1.55 mu m F-P and DFB lasers

Numerical calculations of the second-order harmonic distortion in the amplitude modulation-response of Fabry-Perot, and distributed feedback (DFB) lasers are presented, and the influence of several nonlinearities, such as longitudinal spatial hole burning, gain suppression, and relaxation oscillations are considered. This analysis is valid for modulation frequencies ranging from a few megahertz to well beyond the resonance frequency of the relaxation oscillation. The distortion of Fabry-Perot lasers for which the effects of spontaneous emission and gain suppression can be clearly illustrated is investigated. The distortion of DFB lasers where the emphasis is on the influence of spatial hole burning and its combination with other nonlinearities is discussed. Various effects are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Sensitivity of multiple-phase-shift distributed feedback semiconductor lasers to spatial hole burning

The influence of spatial hole burning on the behaviour of multiple-phase-shift DFB lasers has been analysed. It is found that for values of the phase-shift parameter lower than ∼0.4, the extent of the singlemode regime is seriously reduced owing to a rapid increase of the mode nonuniformity along the cavity length.

On the influence of spatial hole-burning on mode selection and mode synchronization in a CW laser

The influence of spatial saturation modulation of both the amplifier and absorber in a laser with a Fabry-Perot resonator, and of the associated Bragg-reflection, on the frequency-dependent losses necessary for single-frequency operation, as well as on the frequency synchronization of three modes, has been examined. Conditions for mode selection and mode synchronization are given. To achieve single-frequency operation in a laser with a Fabry-Perot resonator the loss difference between the mode to be selected and modes to be quenched has to be proportional to the Bragg losses of the selected mode suffered by its self-induced grating. The proportionality factor depends on the length and position of the amplifier in the cavity. In the case of a short amplifier and a short absorber inside the resonator, the discussion of conditions for synchronization of three modes shows that the synchronization regime is also determined by the position of the absorber.

Influence of spatial hole burning on the output power of a CW dye ring laser

The output power of a single-mode CW dye ring laser can be enhanced by 50 percent by changing over from standing-wave (SW) operation to traveling-wave (TW) operation. This effect is attributed to smoothing out the SW pattern in the active medium, which gives rise to spatial inhomogeneities of the inversion.

The influence of spatial hole-burning in single mode Q-switch operation

The influence of spatial hole-burning effects on the output of Q-switched giant pulse lasers is investigated. Generalised fundamental equations are established and analytically treated to obtain the total output energy and the remaining inversion density. The results are completed by numerical computations which made it possible to obtain the time-dependent output intensity and the width of the pulses. The solutions of the modified equations are compared with earlier calculations where spatial hole-burning has not been included. It is shown that the formation of standing waves inside the cavity leads to a reduction of the total output energy but does not affect the pulse width of the laser emission.