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Amplified Spontaneous Emission is ubiquitous in systems with optical gain and is responsible for many opportunities and shortcomings. Its role in the progression from the simplest form of thermal radiation (single emitter spontaneous emission) all the way to coherent radiation from inverted systems is still an open question. We critically review observations of photon bursts in micro- and nanolasers, in the perspective of currently used measurement techniques, in relation to threshold-related questions for small devices. Corresponding stochastic predictions are analyzed, and contrasted with burst absence in differential models, in light of general phase space properties. A brief discussion on perspectives is offered in the conclusions.

We report on the mid-infrared laser operation of a cubic 15 at.% E r 3 + : K Y 3 F 10 crystal. In the quasi-continuous-wave regime, the peak power reaches 255 mW at 2.80 µm (the 4 I 11 / 2 → 4 I 13 / 2 transition) with a slope efficiency of 10.9% and a laser threshold of 58 mW. Two pumping schemes (to the 4 I 11 / 2 and 4 I 9 / 2 states) are compared. The emission properties of the E r 3 + ions in K Y 3 F 10 are studied, indicating high stimulated-emission cross-section of 0.57 × 10 − 20 c m 2 at 2.80 µm, a large gain bandwidth of 40 nm, and a long 4 I 11 / 2 state lifetime of 4.64 ms.

Recent years have seen an increase of interest in developing nano-scale sources of coherent radiation. Numerous schemes includes novel confinement techniques such as plasmons and micro resonators as well as novel materials, such as two-dimensional transition metal di-chalcogenides have been investigated. In the process a lot of confusion has been produced by introduction into consideration of numerous parameters such as Purcell factor and the beta (fraction of spontaneous emission going into a given mode). That confusion makes comparative analysis of miniature lasers difficult. In this talk we show that the only parameters defining the laser threshold are the modal loss, quantum efficiency and physical volume of gain medium. Using this method we compare the novel lasers with existing state of the art – DFB and VCSELs and draw conclusions.

We report on a watt-level highly efficient europium laser operating at the 5 D 0 → 7 F 4 transition. It is based on the stoichiometric K E u ( W O 4 ) 2 crystal. Under pumping by a green laser at 532.1 nm, the K E u ( W O 4 ) 2 laser generated a maximum peak output power of 1.11 W at ∼ 703 n m with a slope efficiency of 43.2% and a linear polarization ( E ‖ N m ). A laser threshold as low as 64 mW was achieved. True continuous-wave operation was demonstrated. The polarized emission properties of monoclinic K E u ( W O 4 ) 2 were determined.

Enhancement in rotation sensitivity is achieved in a parity–time-symmetric gyroscope consisting of a ring with gain coupled to a lossy ring, operated below laser threshold and in the vicinity of its exceptional point (EP). An external laser and a conventional readout system are used to measure the large rotation-induced shifts in resonance frequency known to occur in this device. A complete model of the rotation sensitivity is derived that accounts for gain saturation caused by the large circulating power. Compared to a single-ring gyro, the sensitivity is enhanced by a factor of ∼ 300 when the inter-ring coupling is tuned to its EP value κ EP , and ∼ 2400 when it is decreased from κ EP , even though the Sagnac frequency shift is then much smaller. ∼ 40 % of this 2400-fold enhancement is assigned to a new sensing mechanism where rotation alters the gain saturation. These results show that this compact gyro has a far greater sensitivity than a conventional ring gyro, and that this improvement arises mostly from the gain compensating the loss, as opposed to the enhanced Sagnac frequency shift from the EP. This gyro is also shown to be much more stable against gain fluctuations than a single-ring gyro with gain.

It is known (yet often ignored) from quantum mechanical or energetic considerations, that the threshold gain of the quasi-static spaser depends only on the dielectric functions of the metal and the gain material. Here, we derive this result from the purely classical electromagnetic scattering framework. This is of great importance, because electrodynamic modelling is far simpler than quantum mechanical one. The influence of the material dispersion and spaser geometry are clearly separated; the latter influences the threshold gain only indirectly, defining the resonant wavelength. We show that the threshold gain has a minimum as a function of wavelength. A variation of nanoparticle shape, composition, or spasing mode may shift the plasmonic resonance to this optimal wavelength, but it cannot overcome the material-imposed minimal gain. Furthermore, retardation is included straightforwardly into our framework; and the global spectral gain minimum persists beyond the quasi-static limit. We illustrate this with two examples of widely used geometries: Silver spheroids and spherical shells embedded in and filled with gain materials.

There is always a special interest in trying to predict transitions, crisis, social revolutions, catastrophic events like the end of the world and, nowadays judging by the number of spam messages coming from clairvoyants, we strongly believe that the interest in predicting events of every type is growing fast. Almost always catastrophic events are produced when a bifurcation occurs in a dynamical system. Examples in optics can be the laser threshold, bistability, optical rogue waves, instabilities in lasers with injected signal, and many other drastic changes in the behavior of a system.

In the talk we will discuss the role of disorder-induced losses on the threshold of line-defect photonic crystal lasers. Experiments reveal an optimum cavity length, on the order of 10 unit cells, where the laser threshold density attains a minimum. The results can be explained by considering the role of slow-light propagation on the threshold of a photonic crystal laser. We will also discuss the possibility of alleviating this dependence on cavity length by replacing one of the mirrors with a narrow-band mirror based on a Fano resonance.

Active laser arrays, of arbitrary pattern, were created by inkjet deposition of self-assembled photonic structures in the form of dye-doped chiral nematic liquid crystals. The print process itself achieves the requisite alignment for photonic band-edge lasing action normal to the substrate; laser threshold and linewidth characteristics are presented.

Random laser actions in a disordered media based on ethylene glycol doped with Rh6G dye and Au nanorods have been demonstrated. It was observed that the size of Au nanorods strongly affects the pump threshold. The experiment results suggesting that the random lasing properties are dominated by the surface plasmons.

CW mirrorless laser operation at 1840 nm at room temperature was observed in buried rib waveguides of KY0.58Gd0.22Lu0.17Tm0.03(WO4)2 fabricated by structuring KY(WO4) substrates by Ar-ion milling and subsequent liquid phase epitaxial growth of the active layer on these substrates. Laser efficiency and laser threshold seems to change with the width of the channels fabricated.

The laser was born on May 16, 1960 at Hughes Research Laboratories in Malibu, California. Instead of enjoying the view of the Pacific from his new office window, Theodore Maiman closeted himself in a windowless lab, where he slipped a spring-shaped photographic flashlamp over a stubby ruby rod, then put the assembly inside a reflective cylinder. Firing pulses with higher and higher voltage through the lamp, he carefully studied oscilloscope traces of the rise and fall of the ruby's red fluorescence. Once the voltage exceeded 950 volts, the lamp flashed bright enough to excite the ruby above laser threshold. The red light suddenly flashed so bright that Maiman's colorblind assistant Irnee D'Haenens saw red light for the first time [1]! The instruments recorded what Maiman had predicted would happen above laser threshold – the pulse rose and fell faster, and the range of red wavelengths narrowed. This article provides an overview of the first 50 years of laser development as well as a brief outlook what's coming next.

A kind of Faraday glass with a size of Φ40 mm × 14 mm and Φ100–300 mm × 25 mm, respectively, was prepared by the melting and casting process, which had neither a Pt particulate nor a bubble or striation. The measurement results showed that the surface homogeneity of the samples was up to ± 1 × 10−6, the laser threshold reached 10 J/cm2 (1ω, 3 ns), and the Verdet constants of the glasses were −0.273 min/Oe/cm at 632.8 nm and −0.076 min/Oe/cm at 1064 nm, respectively.

The microcavity and the influence of nonradiative recombination can control spontaneous emission. An analytic resolution of rate equation is studied for microcavity lasers. The relationship between output properties and structural parameters of multi-quantum wells (MQWs) is obtained. One of the most important consequences of the increased spontaneous emission factor is the reduction of laser threshold. It is found that the characteristic curve of a "thresholdless" laser is strongly nonradiative depopulation-dependent. The light output is increased by the enhanced well number and the reduced width. In particular, there is an optimal well number corresponding to the lowest threshold current density for MQW structure in the microcavity lasers.

Liquid crystal (LC) lasers have gained a lot of research interest in the last decade. Especially out-of-plane emitting chiral nematic liquid crystal (CLC) lasers have been studied extensively. These regular CLC lasers have a one-dimensional (1D) structure and the active cavity length is inherently limited. By using CLCs in two- and three-dimensional structures, the flexibility and applicability of the laser structures can be strongly enhanced. In this paper we focus on 2D in-plane emitting CLC lasers with a lying helix structure. We elaborate further on different techniques to obtain the lying helix structure and we analyze the lasing properties and compare these to regular 1D out-of-plane emitting CLC and NLC lasers. Both differences in emission spectrum, laser threshold, slope efficiency and maximal output energy are discussed.

In the assembly of optical resonators of optically pumped semiconductor lasers (OPSL), the highly reflective resonator mirror is the most crucial component. In previous cooperation, Coherent and Fraunhofer IPT have developed a robust active alignment strategy to optimize the output power of the OPSL resonator using search strategies for finding the laser threshold as well as hill-climbing algorithms for maximizing the output power. Beam-shape as well as the laser mode have major influence on the quality and the duration of subsequent beam-shaping and fiber-coupling steps. Therefore, the alignment algorithm optimizing the output power has been extended recently by simultaneous image processing for ensuring a Gaussian beam as the result of alignment. The paper describes the enhanced approach of automated alignment by additionally scanning along the optical resonator and subsequently evaluating and optimizing the roundness of the beam as well as minimizing the beam radius through twisting and tilting of the mirror. A quality metric combining these measures is defined substituting an M² measurement. The paper also describes the approach for automated assembly including the measuring setup, micromanipulation and dispensing devices.

The absorption spectra of Tb,Tm:YVO4 and Ho,Tm:YVO4 are measured. The radiant and non-radiant transition probabilities from higher level to lower level, Ai,j and ?i,j and the cross-relaxation probability are calculated in virtue of Judd?Ofelt and Dexter theories. The fluorescence lifetime of Tm3+ in the Tb3+ (or Ho3+) co-doped crystal is calculated. It indicates that the lifetime of initial level 3H4 of the laser transition can be shorter than that of terminal level 3F4 of the transition if the atomic percentage of Tb3+ (or Ho3+) ions is bigger than about 1 at%: namely, by means of the co-doping Tb3+ (or Ho3+) ions the self-termination phenomenon of laser light can be eliminated. Inserting the optic parameters to the formula deduced here on the laser threshold power P(4)th and the slope efficiency ?(4)s of the four-energy-level system, we obtain the relationship of threshold power P(4)th to the concentration of Tm3+ ions and discuss the effect of Tb3+ (or Ho3+) ion concentration on the laser threshold power P(4)th around 1.5?m wavelength. The result shows that Tb,Tm:YVO4 crystal is a better choice to make the laser at ~1.5?m wavelength than Ho,Tm:YVO4 crystal. We give the appropriate composition of (1?2) at% Tb, (1?2) at% Tm:YVO4, just for reference.

The dependence of the refractive index and emission line-width of laser crystals on the atomic parameters of ions in the crystals has been analyzed qualitatively. As a result, an empirical relationship between laser threshold and chemical composition of laser crystals is proposed and demonstrated by some oxide crystals. The relation may be useful for the investigations of laser crystals.

We study theoretically the non linear polarization dynamics of Vertical-Cavity Surface-Emitting Lasers in the presence of an external cavity providing delayed optical feedback and cross polarization re-injection. We show that far from the laser threshold, the dynamics remains confined close to the equatorial plane of a Stokes sphere of a given radius and we reduce the dynamics to a dynamical system composed of two phases: the orientation phase of the quasi-linear polarization and the optical phase of the field. We explore the complex modal structure given by the double feedback configuration and recovers as particular cases the Lang-Kobayashi modes and the modes founds by Giudici et al. [1]. We also re-interpret the square waves switching dynamics as phase kinks.

We observed optomechanical oscillations at 384-kHz by immersing a silica microsphere in an aqueous environment. Despite of high dissipation, the device displays a laser threshold power of 0.98-mW and a mechanical Q of 1,648.

We compare orientational relaxation phenomena of a light-emitting polymer and a, spectroscopically similar, conventional laser dye in solutions of comparable viscosity. The orientational relaxation time of the laser dye is found to be very much smaller than that of the polymer. This result is attributed to the large difference in shape between the two light-emitting materials. We demonstrate that these very different reorientation times have a major influence on the operation of a gain-switched laser based on these gain media, in particular on its threshold.

This paper reports the thermal properties and 1·064 m m lasing characteristics of Nd3+:LaVO4 crystal pumped with a Ti:sapphire laser. The maximum laser output power is 107 mW at the pumping power of 461 mW. The slope and light conversion efficiency are 52·8 and 22·9% respectively, and the laser threshold is 45 mW. These results indicate that Nd3+:LaVO4 crystal can be regarded as a new laser crystal.

Energy-transfer processes have been quantitatively studied in various Tm:Yb-doped fluoride crystals. A comparison between the three host crystals which have been examined $({\mathrm{KY}}_{3}{\mathrm{F}}_{10},$ ${\mathrm{LiYF}}_{4},$ and ${\mathrm{BaY}}_{2}{\mathrm{F}}_{8})$ shows clearly that the efficiency of the $\mathrm{Y}\stackrel{\ensuremath{\rightarrow}}{b}\mathrm{Tm}$ energy transfers is larger in ${\mathrm{KY}}_{3}{\mathrm{F}}_{10}$ than in ${\mathrm{LiYF}}_{4}$ or ${\mathrm{BaY}}_{2}{\mathrm{F}}_{8}.$ The dependence of the energy-transfer parameters upon the codopant concentrations has been experimentally measured and compared with the results calculated on the basis of migration-assisted energy-transfer models. Using these energy-transfer parameters and a rate equation model, we have performed a theoretical calculation of the laser thresholds for the ${}^{3}{\stackrel{\ensuremath{\rightarrow}}{{H}_{4}}}^{3}{F}_{4}$ and ${}^{3}{\stackrel{\ensuremath{\rightarrow}}{{H}_{4}}}^{3}{H}_{5}$ laser transitions of the Tm ion around 1.5 and 2.3 \ensuremath{\mu}m, respectively. Laser experiments performed at 1.5 \ensuremath{\mu}m in ${\mathrm{Y}\mathrm{b}:\mathrm{T}\mathrm{m}:\mathrm{L}\mathrm{i}\mathrm{Y}\mathrm{F}}_{4}$ then led to laser threshold values in good agreement with those derived theoretically. Based on these results, optimized values for the Yb and Tm dopant concentrations for typical values of laser cavity and pump modes were finally derived to minimize the threshold pump powers for the laser transitions around 1.5 and 2.3 \ensuremath{\mu}m.

Nd:YLF laser at 908 nm, providing an QCW output power of 6.4 W at 33 W of absorbed pump power and a laser threshold of 3.2 W of absorbed pump power at 797 nm.

This review summarizes recent developments and successes in the theoretical modelling of the characteristics of semiconductor microcavity lasers. After a discussion of the basic laser properties, results of a quasi-equilibrium many-body theory are presented which are very useful for the understanding of microcavity laser operation not too far above the laser threshold. Non-equilibrium phenomena, such as spectral and kinetic hole burning as well as plasma heating effects, are analysed using a quantum kinetic approach. Comparisons with experimental observations are discussed, before open problems and future challenges are outlined.

A scaling law obeyed by photon number fluctuations near threshold in the Ginzberg-Landau theory of second order phase transition is described. Normalized factorial moments are found to scale as F r ∼ F β r 2 , r ⩾ 3. The results from photon counting experiments on laser fluctuations near threshold are shown to support this scaling law. It is found that β r = ( r − 1) v , where v = 1.304. Implication of the scaling behavior is discussed.

We report for the first time on the observation of self-mode-locking in a diode pumped self-Q-switched (SQS) Nd3+,Cr4+:YAG laser. This phenomenon results from significant excited state absorption of the Cr4+ ions in the co-doped host during the SQS laser pulses. The self-mode-locking occurs already slightly above the SQS laser threshold. Experiments using relatively low saturable intensity achieved a modulation depth of more than 40%.

Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-27T11:25:30Z No. of bitstreams: 0Bitstream added on 2014-05-27T14:47:10Z : No. of bitstreams: 1 2-s2.0-79952615742.pdf: 1081751 bytes, checksum: 686fe3218ec563e5b0d170077dd5dbe5 (MD5) Made available in DSpace on 2014-05-27T11:25:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-03-14 An upconversion random laser (RL) operating in the ultraviolet is reported for Nd 3+ doped fluoroindate glass powder pumped at 575 nm. The RL is obtained by the resonant excitation of the Nd 3+ state 2G 7/2 followed by energy transfer among two excited ions such that one ion in the pair decays to a lower energy state and the other is promoted to state 4D 7/2 from where it decays emitting light at 381 nm. The RL threshold of 30 kW/cm 2 was determined by monitoring the photoluminescence intensity as a function of the pump laser intensity. The RL pulses have time duration of 29 ns that is 50 times smaller than the decay time of the upconversion signal when the sample is pumped with intensities below the RL laser threshold. © 2011 Optical Society of America. Departamento de Física Universidade Federal de Pernambuco, 50670-901 Recife, PE Instituto de Química Universidade do Estado de São Paulo, 14801-970 Araraquara, SP

Antiresonant reflecting optical waveguide (ARROW-type) vertical-cavity surface-emitting lasers are designed for high-power single-mode operation. A detailed full-vector finite-difference time-domain (FDTD) study shows strong modal discrimination in favor of the fundamental mode for large aperture (>6 /spl mu/m), large index-step (/spl Delta/n>0.025) simplified ARROW-type devices. The FDTD model identifies the polarization-dependent radiation losses of the higher order modes, which prevent them from reaching laser threshold.

The increase in slope efficiency and the reduction of the laser threshold of a flash-lamp-pumped Ho,Cr,Tm:YAG laser that are due to increased flash-lamp efficiency when the current of the dc simmer is increased are described. Investigations of the electrical characteristics of the flash lamp as a function of the simmer current prove that the flash-lamp impedance decreases to a constant value when the dc simmer current is increased. As a consequence an increase of the peak current through the flash lamp is observed, which improves the flash-lamp efficiency.

We report on whispering gallery mode lasing in electrically driven quantum dot micropillar cavities. The high quality microcavity structures feature whispering gallery mode emission with Q-factors up to 40 000 and laser threshold currents below 10 μA for devices with diameters between 2.6 and 5.6 μm. For large diameter micropillars a coexistence of lasing from two whispering gallery modes is realized which could be the basis for efficient terahertz generation via difference frequency generation.

The two-dimensional theory of a distributed feedback (DFB) laser (which was previously presented and applied to the analysis of the laser threshold conditions for the transverse-electric (TE) mode in a simple three-layer waveguide structure) is developed to treat both TE and transverse-magnetic (TM) modes in a four-layer waveguide structure with a thin grating layer, which more closely reflects actual DFB laser structure. The differences between TE and TM modes for the dispersion relations and the laser threshold conditions are clarified. The effects of the waveguide structure (including grating layer thickness, refractive indexes of layers, coupling constant, and corrugation period) on the threshold gains and the gain differences between the two longitudinal modes on both sides of the Bragg frequencies are studied in detail for both TE and TM modes. >

The prospect of using GaAs nanoneedles as whispering gallery mode resonators is presented. Energy resonances, spatial mode distribution, and laser threshold values of these nanostructures are estimated.

Intensity fluctuations in a pulsed dye laser are studied. Fluctuations are local and very fast. The onset of the fluctuating regime coincides with the laser threshold. The average Fourier spectrum of fluctuations shows three broad peaks at frequencies v1=55 MHz, v2=110 MHz, v3=165 MHz. The three frequencies remain unchanged when resonator geometrical and optical parameters are changed. Nevertheless the amplitude of fluctuations is easily affected by such changes and by the solution temperature. The application of the Grassberger-Procaccia algorithm to the experimental fluctuations gives slope convergence (between 3 and 5) in some cases. This seems to indicate that the origin of fluctuations is chaotic-deterministic.

Ytterbium doped sodium phosphotellurite glasses are made with different Yb 3+ concentrations. Physical properties of the new glasses are reported. The glasses show high absorption and emission cross-sections and higher lifetime of [equation] transition. Laser performance parameter σ e × τ f , with a value as high as 2.14×10 -20 cm 2 -ms and the laser threshold intensity as low as 1.79 KW/cm 2 are reported. The laser parameters of these Yb 3+ doped glasses show that they are potential to fabricate high power laser and broadband optical amplifiers.

In this contribution, microscopic simulation of optical gain in GaN-based short-wavelength lasers is presented. The model is used to perform a design study of different active regions, and to discuss the impact of inhomogeneous broadening, carrier-induced screening of the piezo charges, and well thickness on material gain and laser threshold current. As a reference, the model parameters are calibrated with temperature dependent Hakki-Paoli measurements of spectral gain. Excellent agreement between measurement and simulation is achieved, which gives the design studies a quantitative character.

In this paper, the potential of femtosecond pulse lasers for the cleaning application of sensitive painted artworks are discussed. A comparative study on the ablation rate and threshold of femto- and nano-second laser pulses of typical varnishes (dammar, mastic. etc) and pigments (red and white lead, vermilion, ochres etc.) have been performed

In this paper we resolve the separate contributions of resonant and non-resonant carrier populations to the differential index below threshold. We then apply this understanding to the explanation of index shifts above and below laser threshold as a function of device gain saturation.

Nd:Sr 5 (PO 4 ) 3 F, known as Nd:S-FAP, is a new material for efficient and miniature diode-laser pumped solid-state lasers. By using a laser-diode pump operating at 805.4 nm, Nd:S-FAP has been successfully lased at 1.328 μm. A slope efficiency of 33.5% and a laser threshold of 18.5 mW have been measured. The theoretical formulas for threshold power and slope efficiency were given and the theoretical estimation agreed with the experimental result.

We have studied the laser performance of Nd: KGW and Nd: YAG rods by monitoring the 1.06 μm laser emission at 78.5 K and 300 K. Our observations indicate that the laser efficiency from Nd: KGW is much higher than from Nd: YAG at these two temperatures. The laser threshold in Nd: KGW is lower at 78.5 K than at 300 K but it is always lower than that in Nd:YAG.

We present an experimental study of a Vertical-Cavity Surface-Emitting laser with polarized optical feedback. The system displays single-mode Low Frequency Fluctuations (LFF) for a wide range of pump current. Above the solitary laser threshold we observe a new kind of couple-mode dynamics with a leading LFF behavior in one polarization and an induced pulsed emission in the orthogonal one.

A linear stability analysis of the Lorenz-laser equations taking into account the local field correction is presented. It is demonstrated that this correction lowers the second laser threshold for negative detunings.

The faulty microstructure of KDP samples having different bulk laser damage threshold (4 multiplied by 1010 W/cm2 - 5.4 multiplied by 1011 W/cm2 was studied using the methods of the three-crystal x-ray diffraction and two-crystal topography on reflection. A correlation between the dispersion of the structure-sensitive parameters characterizing the microfaultness and the value of bulk laser threshold of samples cut off large KDP crystals was established.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We studied the cavity solitons (CSs) and their switching in a semiconductor Fabry–Perot type microresonator where the active medium is multiple quantum well nanostructures. We take benefit of the full set of Maxwell–Bloch equations to describe the dynamical behavior of the system, since the rate equation model for a two-level system fails to explain the system when considering femtosecond time scales. Numerical simulations imply formation of stable CSs which is done by local carrier injection as the switching method. To switch off these CSs we used the same method but with negative amplitude of the injection function. It is also realized that the successive switching on/off of CSs by such a scheme is possible in this system.

In this paper we investigated cavity soliton switching in a VCSEL type semiconductor laser which has been driven by homogeneous holding beam. Using quadratic fitting of the gain curve we studied the incoherent switching technique for the controlling of cavity solitons in a VCSEL-type laser and we show the cavity soliton spontaneous mobility in this type of injection.

This paper reviews several topics related to optically pumped ZnO nanowire lasers. A systematic study of the various properties of a device as it evolves from the regime of amplified spontaneous emission to laser oscillation above threshold is presented. The key dependence of the laser threshold on nanowire diameter is demonstrated and explained by means of a thorough study of guided modes in semiconducting nanowires for a nanowire-on-substrate geometry. A 'head on' detection geometry is used to measure the far-field profile of a nanowire laser and thus identify the modes responsible for lasing. Finally, the temperature behavior of a nanowire laser is reported, and possible mechanisms that may be responsible for gain are suggested.

A linear decrease in the 'second laser threshold' is found when two lasers are optically coupled in the bad cavity limit. The coupled lasers are modeled as on-resonance, single mode, homogeneously broadened lasers. In-phase coupling does not cause lasers operating in the good cavity limit to operate chaotically and may make such lasers more stable. The authors observed that out-of-phase coupling of lasers in the good cavity limit can lead to self-pulsing and limit cycles.

Gain spectra of the room temperature ZnSe‐based blue‐green lasers have been measured in index guided, single quantum well (SQW) devices that show a peak gain coefficient at a laser threshold of approximately 1500 cm−1.

Experimental results on the realisation and spectral characterisation of Er-ZBLAN microspherical lasers at 1.56 µm are presented. The laser effect is obtained using the properties of whispering gallery modes and pumping at 1.48 µm. Multimode operation and a laser threshold as low as 600 µW have been observed.

Nd:Sr(5) (PO(4))(3) F, known as Nd:S-FAP, is a new material for efficient, miniature diode-pumped solid-state lasers. By using a laser-diode pump operating at 805.4 nm, we successfully lased Nd:S-FAP at 1.328 mum. A slope efficiency of 33.5% and a laser threshold of 18.5 mW have been measured. By using KTP as an intracavity doubling crystal, we also achieved an intracavity frequency Nd:S-FAP laser at 0.664 mum with a threshold power of 18.2 mW, a TEM(00) mode red laser output power of 20.7 mW at 250 mW incident pump power corresponding to an optical efficiency of 8.3%. In addition, we discuss ways to improve efficiency by use of this material.