Compound-cavity Laser Research Articles

Thermal noise and optomechanical features in the emission of a membrane-coupled compound cavity laser diode.

We demonstrate the use of a compound optical cavity as linear displacement detector, by measuring the thermal motion of a silicon nitride suspended membrane acting as the external mirror of a near-infrared Littrow laser diode. Fluctuations in the laser optical power induced by the membrane vibrations are collected by a photodiode integrated within the laser, and then measured with a spectrum analyzer. The dynamics of the membrane driven by a piezoelectric actuator is investigated as a function of air pressure and actuator displacement in a homodyne configuration. The high Q-factor (~3.4 · 104 at 8.3 · 10−3 mbar) of the fundamental mechanical mode at ~73 kHz guarantees a detection sensitivity high enough for direct measurement of thermal motion at room temperature (~87 pm RMS). The compound cavity system here introduced can be employed as a table-top, cost-effective linear displacement detector for cavity optomechanics. Furthermore, thanks to the strong optical nonlinearities of the laser compound cavity, these systems open new perspectives in the study of non-Markovian quantum properties at the mesoscale.

Electro-optical resonance modulation of vertical-cavity surface-emitting lasers

Optical and electrical investigations of vertical-cavity surface-emitting lasers (VCSEL) with a monolithically integrated electro-optical modulator (EOM) allow for a detailed physical understanding of this complex compound cavity laser system. The EOM VCSEL light output is investigated to identify optimal working points. An electro-optic resonance feature triggered by the quantum confined Stark effect is used to modulate individual VCSEL modes by more than 20 dB with an extremely small EOM voltage change of less than 100 mV. Spectral mode analysis reveals modulation of higher order modes and very low wavelength chirp of < 0.5 nm. Dynamic experiments and simulation predict an intrinsic bandwidth of the EOM VCSEL exceeding 50 GHz.

160 GHz harmonic mode-locked AlGaInAs 155μm strained quantum-well compound-cavity laser

We characterized the reflectivity and the modal discrimination of intracavity reflectors (ICRs) with different numbers of slots and presented harmonic mode-locking operation of a monolithic semiconductor laser comprising a compound cavity formed by a single deeply etched slot ICR fabricated from 1.55 μm AlGaInAs strained quantum well material. Gaussian pulses were generated at a 161.8 GHz repetition rate with a pulse duration of 1.67 ps and a time-bandwidth product of 0.81.

Analysis for the self-mixing interference effects in a laser diode at high optical feedback levels

Based on the study of the self-mixing interference effects at different optical feedback levels, a model is presented in terms of the threshold condition of a compound cavity laser. This model considers the optical feedback effect on the real and imaginary parts of the complex refractive index of the laser active medium and the asymmetric external cavity effect. Complex waveforms experimentally observed at high feedback levels can be interpreted well by this model. Theoretical and experimental results show a potential increase in the resolution of the displacement measurement at a high optical feedback level or misalignment condition.

Tunable operation of a gain-switched diode laser by nonresonant self-injection seeding

We report tunable operation of a gain-switched diode laser by nonresonant self-injection seeding from an uncoated glass slide used as an external cavity reflector. A spectral linewidth reduction from 11 to 0.05 nm has been achieved for picosecond pulses with little effect on other laser characteristics. Good agreement with numerical simulations based on a compound-cavity laser model is also reported.

Terahertz repetition frequencies from harmonic mode-locked monolithic compound-cavity laser diodes

Compound-cavity laser diodes are mode locked at a harmonic of the fundamental round-trip frequency to achieve repetition rates of up to 2.1 THz. The devices are fabricated from GaAs/AlGaAs material at a wavelength of 860 nm and incorporate two gain sections with an etched slot reflector between them, and a saturable absorber section. Autocorrelation studies are used to investigate device behavior for different reflector types and reflectivity. These lasers may find applications in terahertz imaging, medicine, ultrafast optical links, and atmospheric sensing.

Nonresonant self-injection seeding of a gain-switched diode laser

We demonstrate step-tunable single-mode operation of a gain-switched diode laser by nonresonant self-injection seeding from an uncoated glass slide used as an external cavity reflector. A spectral bandwidth reduction from 11 nm to 0.05 nm and wavelength tunability has been achieved for picosecond (near-transform-limited) pulses with little effect on other laser characteristics. Good agreement with numerical simulations based on a compound-cavity laser model is also reported.

Passive harmonic modelocking in monolithic compound-cavitylaser diodes

Passive harmonic modelocking operation of novel compound-cavity laser diodes is demonstrated. The modelocking rates can be readily scaled up into the terahertz domain and enable applications in terahertz imaging, medicine, ultrafast optical links, and atmospheric sensing.

Analysis of harmonic (sub)THz passive mode-locking in monolithic compound cavity Fabry-Perot and ring laser diodes

The authors analyse harmonic mode-locking at (sub)terahertz frequencies in linear Fabry-Perot compound-cavity laser diodes (theoretically), and in ring structures (experimentally and theoretically) and compare these lasers with other constructions used for harmonic mode-locking.

Turn-on transient dynamics in a multimode, compound-cavity laser

The turn-on-time statistics for an individual longitudinal mode and the total intensity of a multimode laser are shown to be very different. In both experiment and theory we find that the differences are due mainly to transitory modes that decay as a result of frequency-dependent losses and gains. Associated with this phenomenon is a kink in the time evolution of the mode intensity, but not in the total intensity, that represents a transition in the dynamics from domination by independent growth of all modes to domination by competition between modes with different net gains. This unequal competition increases the average and the standard deviation of the individual mode turn-on time. The experimental dye-laser system has a thin gain medium (100 µm) that is strongly coupled to a short cavity (2.5 cm) and is adjacent to one of the cavity mirrors. The opposite cavity mirror serves as a relatively weak output coupler. The presence of the thin gain medium in the cavity causes the effective pump and loss rates to be frequency dependent. The result is a transient spectrum in which the cavity modes that have the highest net gain dominate the system more as the turn-on transient progresses. The gain spectrum is found to be strongly affected by the frequency dependence of the compound-cavity modes. Using realistic laser parameters, numerical simulations of a multimode laser model {developed in companion paper [J. Opt. Soc. Am. B14, 191 (1997)]} yield turn-on dynamics and statistics that agree well with those measured experimentally.

Multimode laser model with coupled cavities and quantum noise

A stochastic, semiclassical model is developed for a multimode, homogeneously broadened laser with rapid dipole dephasing, appropriate for semiconductor, Ti:sapphire, or dye lasers. The theory self-consistently incorporates population dynamics including temporal beating effects and relaxation oscillations, spatial hole burning, coherent-wave mixing, and quantum noise. The model is valid for single- and compound-cavity lasers in which the mode frequencies are well defined. We pay particular attention to finding a useful mode basis in the case that the gain medium does not completely fill the cavity. This situation can lead to coupled-cavity effects. For typical systems the model is valid for pump rates up to several times threshold and is tractable for numerical simulations. The theoretical development described in this paper is applied to an experimental system in a companion paper (J. Opt. Soc. Am. B14, 180 (1997)].

Improvement of interference fringes of a laser diode interferometer by controlling chaos with sinusoidally modulated injection

Interference fringes of a laser diode Michelson interferometer are distorted by the external reflection oflight to the laser diode. We demonstrate by a numerical model that one can stabilize the interference fringes by controlling chaos with a sinusoidal modulation of the injection current. We optimized the modulation frequency by referring to an AM power spectrum of the intrinsic fluctuation of a compound-cavity laser diode output and optimized the modulation depth by referring to a bifurcation diagram plotted against modulation depth. The controlled system with optimally tuned sinusoidal modulation is stable with changes in external power reflection. A small perturbation of dc bias of less than 2% can improve the stability of the interference fringes.

Ultrahigh-frequency self-pulsations under gain-switching modulation in 1.5-μm dynamical single-mode monolithic compound-cavity semiconductor lasers: Experiment and theory

The generation of 50-130-GHz high-frequency self-pulsations in ultrafast gain-switched InGaAs-InGaAsP dynamical single-mode monolithic compound-cavity lasers is studied in this paper. With various cavity lengths, the dependence of the pulsation frequency on the length of the respective cavity is shown and analyzed in detail. To explain the observed phenomena, a dynamic theory of the semiconductor laser amplifier is described which takes into account the coherent time-dependent amplification, shortening, and reflection of an incident picosecond optical pulse in the gain-switched amplifier. With the presented model, the theoretical simulation results agree well with the experimental observations.

Spectral characteristics of vertical-cavity surface-emitting lasers with strong external optical feedback

We study the spectral optical properties of vertical-cavity surface-emitting lasers (VCSEL's) in the presence of strong optical feedback from an external reflecting surface. When the feedback strength exceeds 1%, multicompound-cavity-longitudinal-modes are observed. The output spectral width increases significantly as the feedback increases. Besides the normal compound-cavity modes, high-loss compound-cavity modes are also observed for the first time. The experimental observations are well explained by a compound-cavity laser theory.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Inducing periodic oscillations from chaotic oscillations of a compound-cavity laser diode with sinusoidally modulated drive

Inducing periodicity from chaotic oscillations of a compound-cavity laser diode is numerically demonstrated through the Van der Pol model. The deep modulation beyond the limit of the perturbation approximation leads to both turbulence and periodicity. Bifurcation against the modulation frequencies and modulation depth occurs under proper conditions. Therefore it is found that the different periodicity can be induced from chaos by a small change in the frequency and the amplitude of the periodic modulations.

Continuous and discrete wavelength tuning in Er:Yb fiber Fabry–Perot lasers

Continuous and discrete single-frequency tuning in the 1.5-μm wavelength region are demonstrated by incorporation of erbium:ytterbium phosphosilicate fibers in single and compound fiber Fabry–Perot cavity configurations. Continuous wavelength tuning was obtained over 3.3 nm in a single-cavity laser of 218-μm cavity length. Discrete wavelength tuning was achieved over 9.59 nm in a compound-cavity laser having a 2-mm gain section.

Blue light intensity modulation in a frequency doubledtapered amplifiermodelocked laser

Blue light, generated by frequency doubling of a modelocked compound cavity laser based on a tapered GaAlAs amplifier, is modulated by varying the RF modelocking signal amplitude. Switching times are ~20 ns.

Blue light generation using a high power tapered amplifier mode-locked laser

Light at 430 nm is generated by frequency doubling the high peak power output of a mode-locked compound cavity laser based on a tapered GaAlAs amplifier. The laser generated a peak 860 nm power of 12.7 W and pulse energy of 450 pJ. Using a 7.1 mm KNbO3 crystal, 45 mW of average blue light power was produced with a peak power of 1.6 W, minimum pulse length of 8.5 ps, and pulse energy of 30 pJ.

Mode competition and mode locking in compound cavity semiconductor lasers

This letter concerns the mode-competition effect for compound-cavity lasers. Considering the mode properties of such a system we show, that the side cavity mode having the same threshold gain as the lasing one, may correspond to either stable or unstable modes of laser operation. In the last case the mode competition leads to locking of the lasing and side modes yielding high-frequency self-pulsations in some range of the system parameters. This effect can be used for the design of self-pulsating SLs generating optical pulses in the microwave region without an intracavity saturable absorber. >

Influence of external optical feedback on threshold and spectral characteristics of vertical-cavity surface-emitting lasers

We report a study of the effects of external optical feedback on the threshold and spectral characteristics of VCSELs with feedback levels in the range from /spl minus/25 dB to 0 dB. A large threshold current reduction and multi-extended-cavity-mode operation have been observed. The experimental results are in good agreement with the theoretical calculations based on a compound cavity laser model. >