Hole Burning Effect Research Articles

Gain-assisted extraordinary optical transmission through periodic arrays of subwavelength apertures

We theoretically investigate the amplification of extraordinary optical transmission (EOT) phenomena in periodic arrays of subwavelength apertures incorporating gain media. In particular, we consider a realistic structure consisting of an opaque silver film perforated by a periodic array of slits and clad on each side by an optically pumped dielectric thin film containing rhodamine dye molecules. By solving the semiclassical electronic rate equations coupled to rigorous finite-element simulations of the electromagnetic fields, we show how the resonant electric-field enhancement associated with EOT properties enables complete ohmic loss compensation at moderate pump intensity levels. Furthermore, our calculations show that, as a consequence of the strong spatial hole-burning effects displayed by the considered structures, three separate regimes of operation arise: the system can behave as an absorber, an optical amplifier or a laser, depending on the value of the pump intensity. A discussion on the feasibility of reaching the lasing regime in the considered class of structures is also presented.

Time-Domain Large Signal Investigation on Dynamic Responses of the GDCC Quarterly Wavelength Shifted Distributed Feedback Semiconductor Laser

A numerical investigation on the dynamic large-signal analysis using a time-domain traveling wave model of quarter wave-shifted distributed feedback semiconductor lasers diode with a Gaussian distribution of the coupling coefficient (GDCC) is presented. It is found that the single-mode behavior and the more hole-burning effect corrections of quarter wave-shifted distributed feedback laser with large coupling coefficient can be improved significantly by this new proposed light source.

Improved performance of complex gain-coupled DFB laser by using tapered grating structure

In this paper, theoretical analysis of antireflection complex gain coupled distributed feedback lasers (CGC-DFB) with tapered grating structure has been presented. Two types of gratings, convex and concave tapered grating with longitudinal variable depth, in active layer have been proposed. Evaluation of flatness parameter variation above threshold condition shows that concave tapered grating improves the stability of CGC-DFB laser against spatial hole burning (SHB) effect. The dependencies of output power, side mode suppression ratio (SMSR) and oscillation wavelength of CGC-DFB laser on convex and concave grating parameters have been studied. Both convex and concave tapered grating CGC-DFB structures have higher output power than conventional CGC-DFB lasers with uniform grating. It is found that, concave tapered grating structure with parameters p0 = 15 nm and a0 = 0.7 nm has minimum flatness parameter, stable lasing wavelength and flat SMSR profile as a function of current. Theoretical calculation model is based on the numerical solution of coupled wave equations and carrier rate equation by using transfer matrix method. In numerical calculation SHB effect has been assumed.

Beam steering and lateral hole burning in mid‐infrared quantum‐ cascade lasers

AbstractWe investigated the beam‐steering phenomenon of quantum‐cascade lasers emitting at ∼7.8 µm wavelength, operated in pulsed mode at heat sink temperatures around room‐temperature. The lasers have a dimension of 12 µm × 1500 µm. The observed beam‐steering phenomenon has been explained by considering spatial hole burning in the population inversion of conduction electrons along the lateral direction. Rate equations have been set up to describe the lateral hole burning effect. The simultaneous oscillation of at least two lateral modes, which are a consequence of the lateral hole burning and at the same time possible cause of beam steering, has been verified by high‐resolution spectroscopy. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Switchable multi-wavelength fiber ring laser using a side-leakage photonic crystal fiber based filter

A switchable multi-wavelength fiber ring laser is proposed and experimentally demonstrated with a novel side-leakage photonic crystal fiber (SLPCF) based filter incorporated into the ring cavity at room temperature. Stable multi-wavelength laser operations can be achieved due to the spatial mode beating, polarization hole burning and spectral hole burning effects. By adjusting the polarization controller appropriately, the laser can be switched among the single-, dual- and triple-wavelength lasing oscillations whose signal-to-noise ratio is up to 50 dB. In addition, the lasing wavelength can be also tuned and switched by applying the strain to the filter.

Mathematical rigorous approach to simulate an over-threshold VCSEL operation

Mathematical rigorous approach to simulate an over-threshold steady-state operation of vertical-cavity surface-emitting diode lasers (VCSELs) is presented. The proposed approach does not require more parameters than the standard threshold one. With its aid, VCSEL operating conditions exceeding the lasing threshold may be examined. In particular, it enables a computer simulation of an excitation of successive transverse modes when the operation current (applied voltage) is gradually increased, taking into account the spatial hole-burning effect. Hence, using the proposed approach, VCSEL mode selectivity and conditions necessary to maintain a desired single-fundamental-mode operation may be examined for a VCSEL design under consideration.

Wideband-tunable nanotube Q-switched low threshold erbium doped fiber laser

An all-fiber passively wideband-tunable nanotube Q-switched low threshold erbium doped fiber laser is presented. With a low insertion loss carbon nanotube based saturable absorber, C- and L-band tunable Q-switched lasers are achieved by tuning the transmission wavelength of one C-band tunable filter and the other L-band one, respectively. The threshold of the Q-switched operation is only 12.8 mW. The self-mode-locking effect on the Q-switching can be effectively reduced by introducing a spatial hole burning effect with two optical circulators. The tunable wavelength range of the Q-switching laser can be changed by inserting a variable optical attenuator in the laser cavity to tune the gain spectrum.

Scattering-based hole burning mediated by localized surface plasmon resonance in photoreactive random media containing Ag nanoparticles

Photoreactive random media containing silver nanoparticles (Ag NPs) have been fabricated, and hole burning effects based on the interference of multiply scattered light have been investigated. Through the analysis of hole profiles, transport mean free path ℓ is estimated for the light with the wavelength of 585 nm. We find that ℓ in the samples embedded with Ag NPs is much shorter compared with that in a medium containing the same amount of titania (TiO2) NPs, indicating that Ag NPs scatter 585 nm lightwaves much stronger than TiO2 NPs because of their larger scattering cross sections due to the localized surface plasmon resonance.

Lamb-Dip Laser-Induced Fluorescence Spectroscopy for Measuring Magnetic Field in a Plasma

We have developed a Lamb-dip laser-induced fluorescence (LIF) system to precisely measure the local magnetic field strength in a plasma. Utilizing the hole burning effect, we made sharp dips on the LIF spectrum as the frequency markers and accurately determined the Zeeman splitting by reading the frequency interval of the dips. The method is valid even in the conditions where the Doppler broadening of the LIF spectrum is larger than the Zeeman shift. The newly developed LIF system is capable of determining a magnetic field strength on the order of 10-4 T. It has been demonstrated that the Lamb-dip LIF system can successfully reproduce a very small field inhomogeneity in the HYPER-I linear device.

Spatial hole burning in high-power edge-emitting lasers: A simple analytical model and the effect on laser performance

A simple analytical model for the longitudinal distributions of photon and carrier densities in edge-emitting semiconductor lasers significantly above threshold is presented. It is shown that under the conditions considered, the shape of these distributions does not depend on pumping current. Good agreement with previous numerical and seminumerical investigations is obtained. It is shown that any direct effect of longitudinal spatial hole burning on the output power is seen only at very low output mirror reflectances and even then is weak, implying that the main effects of longitudinal nonuniformity are indirect ones, through carrier leakage.

Effects of spatial hole burning in 888 nm pumped, passively mode-locked high-power Nd:YVO4 lasers

We report on an experimental study of 888 nm pumped, passively mode-locked, high-power Nd:YVO4 lasers with an enhanced cavity design, involving spatial hole burning (SHB) in the active medium. We observed a significant pulse shortening due to the concept of “Gain-at-the end,” despite using long gain length up to 30 mm. A 31.6 W average output power TEM00 Nd:YVO4 oscillator, providing 16.2 ps pulses at an repetition rate of 96 MHz is presented. The pulse duration turns out to be primarily a function of the effective gain length, which can be explained by means of SHB. A further pulse shortening with decreasing gain length down to 9.5 ps at 11.1 W average output power is demonstrated.

增益平坦掺铒光纤放大器中均匀信号强度造成的光谱烧孔效应

Spectral hole burning (SHB) effects in a gain-flattened erbium-doped fiber amplifier (EDFA) are demonstrated to be significant in the presence of large signal power around the 1530?1532-nm wavelength range. These are the first effects reported in a setup employing equivalent power level distribution of 40 channels ranging from 1530 to 1561 nm. To explain this, the introduction of a new local population variable into the laser equation is required to support the original inversion ratio that is determined by the pump lasers. In the analysis section, spectroscopic parameters and high signal powers are considered to be other contributing parameters to the change in the gain characteristics. An improvement to this theoretical basis is suggested by implementing mathematical modeling to validate similarities between the gain shape of simulation to that obtained in the experiment.

Nonlinear Operation of a 2-D Triangular Lattice Photonic Crystal Laser

In this paper, an approximate method is presented for the analysis of 2-D triangular lattice photonic crystal laser operation above the threshold. Our approach is based on coupled wave equations, including gain saturation and spatial hole burning effects, and energy theorem. An expression is derived for the small signal gain coefficient for transverse magnetic modes as a function of the output power, losses, coupling strength depending on the shape of the primitive cell of a photonic crystal as well as the index contrast. The laser characteristics obtained reveals optimal coupling strength, for given structure parameters, for which maximal power efficiency of the laser structure is obtained.

Spectral hole burning effects initiated by uniform signal intensities in a gain-flattened EDFA

Spectral hole burning effects initiated by uniform signal intensities in a gain-flattened EDFA

7.5 W Nd:GdVO4环形腔单频激光器

A Nd:GdVO4 crystal is end-pumped by a fiber-coupled laser diode(FCLD), and high power of single-frequency laser output is achieved. The four-mirror bow-tie ring cavity with a Faraday rotator and a half wave plate is applied to eliminate the spatial hole-burning effect. A solid etalon is inserted into the cavity to obtain single-frequency1063 nm output of the narrow line width. The maximum output is7.57 W and the optical-optical conversion efficiency is41.8% with18.10 W of the incident power.

Controlling number of lasing modes for designing short-cavity self-mode-locked Nd-doped vanadate lasers

A short-cavity Nd:YVO4 laser is employed to confirm that a spontaneous mode locking (SML) typically occurs without employing an extra nonlinearity. We further experimentally demonstrate that reducing the number of longitudinal lasing modes can diminish the phase fluctuation and effectively improve the SML pulse stability. Considering the spatial hole-burning (SHB) effect, an analytical expression is derived to accurately estimate the number of longitudinal lasing modes for a practical design guideline.

Management of the high-order mode content in large (40 μm) core photonic bandgap Bragg fiber laser

Very large-mode-area Yb(3+)-doped single-mode photonic bandgap (PBG) Bragg fiber oscillators are considered. The transverse hole-burning effect is numerically modeled, which helps properly design the PBG cladding and the Yb(3+)-doped region for the high-order mode content to be carefully controlled. A ratio of the Yb(3+)-doped region diameter to the overall core diameter of 40% allows for single-mode emission, even for small spool diameters of 15 cm. Such a fiber was manufactured and subsequently used as the core element of a cw oscillator. Very good beam quality parameter M(2)=1.12 and slope efficiency of 80% were measured. Insensitivity to bending, exemplified by the absence of temporal drift of the beam, was demonstrated for curvature diameter as small as 15 cm.

Switchable dual-wavelength polarization-maintaining erbium-doped fiber laser using an optical circulator as the all-reflecting mirror

A simple and effective switchable dual-wavelength polarization-maintaining erbium-doped fiber laser is proposed and demonstrated. Only using a uniform fiber Bragg grating written directly in a segment of the photosensitive and polarization-maintaining erbium-doped fiber as the wavelength selector and an optical circulator as the all-reflecting mirror, a stable simultaneous dual-wavelength oscillation is achieved with a wavelength spacing of 0.364 nm experimentally by exploiting the polarization hole burning effect at room temperature. The output can be switched between single- and dual-wavelength by adjusting the polarization controller. The 3-dB bandwidth and the side mode suppression ratio of the laser’s outputs are measured to be less than 0.01 nm and more than 50 dB. The power fluctuation and wavelength drift are measured to be less than 0.50 dB and 0.020 nm over an hour.

Switchable dual-wavelength erbium-doped fiber laser based on the photonic crystal fiber loop mirror and chirped fiber Bragg grating

The switchable dual-wavelength erbium-doped fiber laser (EDFL) with a two-mode photonic crystal fiber (PCF) loop mirror and a chirped fiber Bragg grating (CFBG) at room temperature is proposed and experimentally demonstrated. The two-mode PCF loop mirror is formed by inserting a piece of two-mode PCF into a Sagnac loop mirror, with the air-holes of the PCF intentionally collapsing at the splices. By adjusting the state of the polarization controller (PC) appropriately, the laser can be switched between the stable single- and dual-wavelength operations by means of the polarization hole burning (PHB) and spectral hole burning (SHB) effects.

10.1007/s11449-008-1013-1

It is shown that the effect of hole-burning under conditions of coherent population oscillations as well as the pulse delay in a saturable absorber (a modification of the slow light effect) can be interpreted, in a comprehensive way, in terms of {\it intensity spectrum} of the and {\it intensity-related susceptibility} of the non-linear medium. The physical content of these effects is illustrated by a simple electric circuit with a non-linear resistor which realizes a full analog of the saturable absorber. In this case the effect of hole-burning in the absorption spectrum of the medium is converted in to the effect of hole-burning in the frequency dependence of resistance of the non-linear resistor and the effect of slow light -- in to the effect of slow current.