We report on a methodology for the evaluation of the DC characteristics, small-signal frequency response and large-signal dynamic response of carrier and photon density responses in semiconductor laser diodes. A single mode laser is considered and described with a pair of rate equations containing a novel non-linear gain compensation term depending on a single parameter that can be chosen arbitrarily. This approach can be applied to any type of solid-state laser as long as it is described by a set of rate equations.
An all optical set-reset flip flop is presented that is based on two coupled identical laser diodes. The lasers are coupled so that when one of the lasers lases it quenches lasing in the other laser. The state of the flip flop is determined by which laser is currently lasing. Rate equations are used to model the flip flop and obtain steady state characteristics. The flip flop is experimentally demonstrated by use of antireflection coated laser diodes and free space optics.
We report the realization of the continuous wave laser emission in the orange at 607 nm from a Pr:BaY2F8 (Pr:BYF) crystal pumped by a blue GaN laser diode. A maximal output power of 78 mW is obtained in a quasi single transverse mode beam. The effect of reabsorption losses at the laser wavelength is also evidenced
The frequency of a 700mW monolithic non-planar Nd:YAG ring laser (NPRO) depends with a large coupling coefficient (some MHz/mW) on the power of its laser-diode pump source. Using this effect we demonstrate the frequency stabilization of an NPRO to a frequency reference by feeding back to the current of its pump diodes. We achieved an error point frequency noise smaller than 1mHz/sqrt(Hz), and simultaneously a reduction of the power noise of the NPRO by 10dB without an additional power stabilization feed-back system.
Injection locking of diode lasers is commonly used to amplify low power laser light, but is extremely sensitive to perturbations in the laser current and temperature. To counter such perturbations, active stabilization is often applied to the current of the injection locked diode. We observe that the diode laser's polarization extinction ratio (PER) greatly increases when injection locked, and therefore the PER provides a measure of injection lock quality. We report robust active stabilization of a diode laser injection lock based on the PER, demonstrating the technique at 399 nm wavelength wh…
We describe passive phase-locking architectures based on external-cavity setups to improve the brightness of diode laser bars. Volume Bragg gratings are used to stabilize the lase line. Numerical modelling and experimental results will be presented.
We demonstrate yellow laser emission using silicate glass fiber as the gain medium. By employing core pumping using widely available GaN diode lasers with emission at 445 nm, we show that Dy3+-doped aluminosilicate glass fiber can be readily excited creating sufficient gain at 581 nm. In this proof of concept demonstration, the maximum output power generated was 3 mW with a slope efficiency approximately 1.8% with respect to injected pump.
Detailed polarization properties have been examined in laser-diode-pumped (LD-pumped) micro-grained ceramic Nd:YAG lasers in different microchip cavity configurations. Stable linearly-polarized single-frequency oscillations, whose polarization direction coincide with that of an LD pump light, were observed in an external cavity scheme. While, in the case of a thin-slice laser scheme with coated reflective ends, elliptically-polarized single-frequency operations took place in the low pump-power regime and dynamic instabilities appeared, featuring self-induced antiphase modulations among counter…
We report ultra-stable locking of a commercially available extended cavity diode laser to a vibration-insensitive high finesse Fabry-Perot cavity. A servo bandwidth of 2 MHz is demonstrated. The absolute stability of the diode laser after locking is measured with a three-cornered-hat method. The resulting Allan deviation reaches a level of $2.95\times10^{-15}$ at 1 s, corresponding to only 0.93 Hz linewidth, even without vibration isolation of the reference cavity.
Frequency comb assisted diode laser spectroscopy, employing both the accuracy of an optical frequency comb and the broad wavelength tuning range of a tunable diode laser, has been widely used in many applications. In this letter we present a novel method using cascaded frequency agile diode lasers, which allows extending the measurement bandwidth to 37.4 THz (1355 to 1630 nm) at MHz resolution with scanning speeds above 1 THz/s. It is demonstrated as a useful tool to characterize a broadband spectrum for molecular spectroscopy and in particular it enables to characterize the dispersion of inte…
We show the abundance of Exceptional Points in the generic asymmetric configuration of two coupled diode lasers, under nonzero optical detuning and differential pumping. We pinpoint the location of these points with respect to the stability domains and the Hopf bifurcation points, in the solution space as well as in the space of experimentally controlled parameters.
We studied complex lasing pattern formations in a thin-slice solid-state laser with wide-aperture laser-diode end-pumping. Radial and rectangular vortex arrays were found to be formed in a controlled fashion with symmetric and asymmetric pump beam profiles, respectively. Most of these vortices exhibited single-frequency oscillations arising from a spontaneous process of transverse mode locking of nearly degenerate modes assisted by the laser nonlinearity. Single-frequency rectangular array beams consisting of a large number of vortices, e.g., closely packed 36 or 46 vortex pixels, were generat…
High-power, diffraction-limited organic solid-state laser operation has been achieved in a vertical external cavity surface-emitting organic laser (VECSOL), pumped by a low-cost compact blue laser diode. The diode-pumped VECSOLs were demonstrated with various dyes in a polymer matrix, leading to laser emissions from 540 nm to 660 nm. Optimization of both the pump pulse duration and output coupling leads to a pump slope efficiency of 11% for a DCM based VECSOLs. We report output pulse energy up to 280 nJ with 100 ns long pump pulses, leading to a peak power of 3.5 W in a circularly symmetric, d…
We demonstrate a simple, compact, and cost-effective laser noise reduction method for stabilizing an extended cavity diode laser to a 3x105 finesse mirror Fabry-Pérot (F-P) cavity corresponding to resonance linewidth of 10 kHz using a crystalline MgF2 whispering gallery mode microresonator (WGMR). The laser linewidth is reduced to sub-kHz such that a stable Pound-Drever-Hall (PDH) error signal is built up. The wavelength of the pre-stabilized laser is tunable within a large bandwidth covering the high reflection mirror coating of a F-P supercavity.
We realize a fiber Bragg grating InGaN based laser diode emitting at 400 nm and demonstrate its high coherency. Thanks to the fabrication of a narrow band fiber Bragg grating in the near-UV, we can reach single-mode and single-frequency regimes for the self-injection locked diode. The device exhibits 44 dB side-mode-suppression-ratio and mW output power. Detailed frequency noise analysis reveals sub-MHz integrated linewidth and 16 kHz intrinsic linewidth. Such a narrow linewidth laser diode in the near-UV domain with a compact and low-cost design could find applications whenever coherency and …
We report on the spectral properties of a diode laser with a tunable external cavity in integrated optics. Even though the external cavity is short compared to other small-bandwidth external cavity lasers, the spectral bandwidth of this tunable laser is as small as 25 kHz (FWHM), at a side-mode suppression ratio (SMSR) of 50 dB. Our laser is also able to access preset wavelengths in as little as 200 us and able to tune over the full telecom C-band (1530 nm - 1565 nm).
We demonstrate passive harmonic mode-locking of a quantum well laser diode designed to support a discrete comb of Fabry-Perot modes. Spectral filtering of the mode spectrum was achieved using a non-periodic patterning of the cavity effective index. By selecting six modes spaced at twice the fundamental mode spacing, near-transform limited pulsed output with 2 ps pulse duration was obtained at a repetition rate of 100 GHz.
Narrow linewidth lasers and optical frequency combs generated with mode-locked lasers revolutionized optical frequency metrology. The advent of soliton Kerr frequency combs in compact crystalline or integrated ring optical microresonators opens new horizons for applications. These combs, as was naturally assumed, however, require narrow-linewidth single-frequency pump lasers. We demonstrate that a regular multi-frequency Fabry-Perot laser diode self-injection locked to an optical whispering gallery mode (WGM) microresonator can be first efficiently transformed to a single-frequency ultra-narro…
1.1 kW, 100 Hz room-temperature diode-pumped nanosecond laser by water immersion cooling
Tsinghua University（清华大学）；State Key Laboratory of Precision Space-time Information Sensing Technology（精密时空信息传感技术全国重点实验室）；Key Laboratory of Photonic Control Technology (Tsinghua University), Ministry of Education（教育部光子控制技术重点实验室（清华大学））
Continuous-wave mode-locked femtosecond 2 um solid-state laser with a c-cut Tm:CaYAlO4 as gain medium was experimentally demonstrated. The mode locked laser generated stable pulses with average output power as high as 531 mW, pulse duration of 496 fs, and repetition rate of 97 MHz at 1975 nm. The research results show that Tm:CaYAlO4 is an excellent gain medium for femtosecond pulse generation at 2um wavelength.
Stable 30 fs pulses centered at 1068 nm (less than 10 optical cycles) are demonstrated in a diode pumped Yb:CaYAlO4 laser by using high-quality chemical vapor deposited monolayer graphene as the saturable absorber. The mode locked 8.43 optical-cycle pulses have a spectral bandwidth of ~ 50 nm and a pulse repetition frequency of ~ 113.5 MHz. To our knowledge, this is the shortest pulse ever reported for graphene mode-locked lasers and mode-locked Yb-doped bulk lasers. Our experimental results demonstrate that graphene mode locking is a very promising practical technique to generate few-cycle op…
An extended cavity diode laser operating in the Littrow configuration emitting near 657 nm is stabilized via its injection current to a reference cavity with a finesse of more than 10^5 and a corresponding resonance linewidth of 14 kHz. The laser linewidth is reduced from a few MHz to a value below 30 Hz. The compact and robust setup appears ideal for a portable optical frequency standard using the Calcium intercombination line.
We describe an efficient laser emission from a directly grown Er3+:YAG single-crystal fiber that is resonantly pumped using a continuous-wave (CW) laser diode at 1532 nm. In a longitudinal pumping, it emits 12.5 W at 1645 nm with a slope efficiency of 32%, which is the highest ever reported for a directly grown Er:YAG single-crystal fiber laser. Using an off-axis pumping scheme, CW output powers up to 7.3 W can be reached and in Q-switched operation, the laser produces 2 mJ pulses with a duration of 38 ns at the repetition rate of 1 kHz with an M^{2} factor below 1.8. To our knowledge this is …
An external-cavity diode laser is reported with ultralow noise, high power coupled to a fiber, and fast tunability. These characteristics enable the generation of an optical frequency comb in a silica micro-resonator with a single-soliton state. Neither an optical modulator nor an amplifier was used in the experiment. This demonstration greatly simplifies the soliton generation setup and represents a significant step forward to a fully integrated soliton comb system.
We demonstrated a 967 nm diode end-pumped Er:GSGG laser operated at 2.794 Micrometer with spectrum width 3.6 nm in the continuous wave(CW) mode. The maximum output power of 440 mW is obtained at an incident pumping power of 3.4 W, which corresponds to an optical-to-optical efficiency of 13% and slope efficiency of 13.2%. The results suggest that short cavity and efficient cooling setup for crystal are advantageous to improve laser performance.
The generation of optical frequency combs via direct electrical pumping of semiconductor lasers is an attractive alternative to the well-established mode-locked laser sources in terms of compactness, robustness and integrability. However, the high chromatic dispersion of bulk semiconductor materials can prevent the generation of frequency combs or lead to undesired pulse lengthening. In this letter, we present a novel dual waveguide for intracavity dispersion compensation in semiconductor lasers. We apply the concept to a short mid-infrared wavelength quantum cascade laser operating in the fir…
A Schottky diode integrated into a terahertz quantum cascade laser waveguide couples directly to the internal laser fields. In a multimode laser, the diode response is correlated with both the instantaneous power and the coupling strength to the diode of each lasing mode. Measurements of the rectified response of diodes integrated in two quantum cascade laser cavities at different locations indicate that the relative diode position strongly influences the laser-diode coupling.
Broad area laser diodes are attractive for the high optical power they can produce. Unfortunately, this high power normally comes at the cost of severely reduced spatial coherence since the wide area of the semiconductor wave-guide is inherently spatially multi-mode (in the slow axis). We demonstrate a method to majorly improve the spatial coherence of a high-power broad-area diode laser by placing it in an external cavity that is mode selective. We design the cavity, such that the diode aperture acts as its own spatial filter, obviating the need for an intra-cavity slit-filter, and optimally …
We present a traveling wave model for a semiconductor diode laser based on quantum wells. The gain model is carefully derived from first principles and implemented with as few phenomeno- logical constants as possible. The transverse energies of the quantum well confined electrons are discretized to automatically capture the effects of spectral and spatial hole burning, gain asym- metry, and the linewidth enhancement factor. We apply this model to semiconductor optical amplifiers and single-section phase-locked lasers. We are able to reproduce the experimental re- sults. The calculated frequenc…
We present a simple method for narrowing the intrinsic Lorentzian linewidth of a commercial ultraviolet grating extended-cavity diode laser (TOPTICA DL Pro) using weak optical feedback from a long external cavity. We achieve a suppression in frequency noise spectral density of 20 dB measured at frequencies around 1 MHz, corresponding to the narrowing of the intrinsic Lorentzian linewidth from 200 kHz to 2 kHz. The system is suitable for experiments requiring a tunable ultraviolet laser with narrow linewidth and low high-frequency noise, such as precision spectroscopy, optical clocks, and quant…
We numerically investigate the complex nonlinear dynamics for two independently coupled laser systems consisting of (i) mutually delay-coupled edge emitting diode lasers and (ii) injection-locked quantum nano-structures lasers. A comparative study in dependence on the dynamical role of alpha parameter, which determine the phase-amplitude coupling of the optical field, in both the cases is probed. The variation of alpha lead to conspicuous changes in the dynamics of both the systems, which are characterized and investigated as a function of optical injection strength for the fixed coupled-cavit…
We report a singly resonant continuous-wave optical parametric oscillator (SRO), which is pumped by a semiconductor laser system and operates in the mid-infrared region (2.9 to 3.6 μm). Fast tuning of the mid-infrared output wavelength by more than 200 nm is demonstrated by scanning the pump laser wavelength through only 1.25 nm, without any need to adjust the SRO settings. The exceptionally large tuning range is obtained by choosing a pump wavelength (780 nm) that corresponds to a turning point of the group velocity mismatch between the phase-matched signal and idler waves of the SRO.
A room temperature operating Vertical External Cavity Surface Emitting Laser is applied around 1550 nm to intracavity laser absorption spectroscopy analyzed by time-resolved Fourier transform interferometry. At an equivalent pathlength of 15 km, the high resolution spectrum of the semiconductor disk laser emission covers 17 nm simultaneously. A noise equivalent absorption coefficient at one second averaging equal to 1.5 10^{-10} cm^{-1}.Hz^{-1/2} per spectral element is reported for the 65 km longest path length employed.
Harmonic and Intermodulation distortions occur when a physical system is excited with a single or several frequencies and when the relationship between the input and output is non-linear. Working with non-linearities in the Frequency domain is not straightforward specially when the relationship between the input and output is not trivial. We outline the complete derivation of the Harmonic and Intermodulation distortions from basic principles to a general physical system. For illustration, the procedure is applied to the Single Mode laser diode where the relationship of input to output is non-t…
Broad aperture semiconductor lasers usually suffer from low spatial quality of the emitted beams. Due to the highly compact character of such lasers the use of a conventional intra-cavity spatial filters is problematic. We demonstrate that extremely compact Photonic Crystal spatial filters, incorporated into the laser resonator, can improve the beam spatial quality, and correspondingly, increase the brightness of the emitted radiation. We report the decrease of the M2 from 47 down to 28 due to Photonic Crystal spatial intra-cavity filtering, and the increase of the brightness by a factor of 1.…
In this paper, we present an experimental study of the metrological stabilization of a solid-state frequency comb for embedded metrology applications. The comb is a passively mode-locked laser diode based on InGaAs/InP Quantum-dash structure emitting optical lines into a 9 nm bandwidth centered at 1.55 $μ$m with a repetition rate of 10.09 GHz. The frequency stabilization is achieved by optical injection locking of the comb with an external cavity laser diode referenced onto a metrological frequency standard. One observes the transfer of the spectral purity from the injection laser to the neigh…
While being invented for precision measurement of single atomic transitions, frequency combs have also become a versatile tool for broadband spectroscopy in the last years. In this paper we present a novel and simple approach for broadband spectroscopy, combining the accuracy of an optical fiber-laser-based frequency comb with the ease-of-use of a tunable external cavity diode laser. This scheme enables broadband and fast spectroscopy of microresonator modes and allows for precise measurements of their dispersion, which is an important precondition for broadband optical frequency comb generati…
The characteristics of mid-infrared laser diodes have been investigated before and after the patterning of sub-wavelength metallic apertures on the emitting facet. Before modification of the facet the emitted spectrum consisted of a large number of peaks associated with different spatial modes, whereas afterwards the spectrum was dominated by a single peak. Simulations showed that the patterning of the facet caused the effective reflectivity to be different for each lateral mode, suggesting that the peak in the measured spectra is associated with the single lateral mode which is most strongly …
We present an entirely fiber based laser source for non-linear imaging with a novel approach for multi-color excitation. The high power output of an actively modulated and amplified picosecond fiber laser at 1064 nm is shifted to longer wavelengths by a combination of four-wave mixing and stimulated Raman scattering. By combining different fiber types and lengths, we control the non-linear wavelength conversion in the delivery fiber itself and can switch between 1064 nm, 1122 nm, and 1186 nm on-the-fly by tuning the pump power of the fiber amplifier and modulate the seed diodes. This is a prom…
We report ultra-low phase-noise microwave generation at a 9.6 GHz carrier frequency from optical frequency combs based on diode-pumped solid-state lasers emitting at telecom wavelength and referenced to a common cavity-stabilized continuous-wave laser. Using a novel fibered polarization-maintaining pulse interleaver, a single-oscillator phase-noise floor of -171 dBc/Hz has been measured with commercial PIN InGaAs photodiodes, constituting a record for this type of detector. Also, a direct optical measurement of the stabilized frequency combs timing jitter was performed using a balanced optical…
We study the injection locking bistability of a specially engineered two-color semiconductor Fabry-Perot laser. Oscillation in the uninjected primary mode leads to a bistability of single mode and two-color equilibria. With pulsed modulation of the injected power we demonstrate an all-optical memory element based on this bistability, where the uninjected primary mode is switched with 35 dB intensity contrast. Using experimental and theoretical analysis, we describe the associated bifurcation structure, which is not found in single mode systems with optical injection.
We report on the generation of 500 mW of spectrally pure laser light at the 460.86 nm transition used for laser cooling of strontium atoms. To this end we inject a high power single mode laser diode with light from a stabilized extended cavity diode laser. To optimize and monitor the injection status and the spectral purity of the slave diode we developed a novel technique that uses a single passive optical element. A narrow band interference filter generates a suitable monitoring signal without any additional electronics for post processing of the data. Our method greatly simplifies the daily…
A highly stable diode-pumped circulation-free liquid dye laser in a vertical external cavity is reported. The design is simple (no fabrication process step required, no fluid circuitry), compact (~ cm sized), and cost-effective. An optical efficiency of 18% with a M${}^2$ of 1 are reported, with an excellent photostability-no efficiency drop was seen after 1.4 million pulses at 50 Hz, a value comparable to flowing systems and much higher than values achievable with organic solid-state lasers. We show that thermal effects are central in the stability and also on the dynamics of this laser. The …
We present a stable dual-wavelength vortex beam carrying orbital angular momentum (OAM) with two spectral peaks separated by a few terahertz in diode-pumped Yb:CaGdAlO4 (CALGO) laser. The dual-wavelength spectrum is controlled by the pump power and off-axis loss in laser resonator, arising from the broad emission bandwidth of Yb:CALGO. The OAM beam is obtained by a pair of cylindrical lens that serves as an π/2 convertor for the high-order Hermite-Gaussian modes. The stability is verifed that the 1 h OAM beam with two spectral peaks at 1046.1 nm and 1057.2 nm (3.01 THz interval) can steadily o…
A chaos-based communication scheme allowing simultaneous bidirectional message transmission (Opt. Lett. 32, 403, 2007) is investigated numerically. Incoherent feedback and coupling case is analyzed, which is expected in real long-distance optical communication systems. It is shown that identical synchronization of chaotic laser waveforms and bidirectional message transmission are possible as in the coherent coupling case. However, the chaotic regime at incoherent feedback and coupling is quite different. It is regular destabilized relaxation oscillations with the chaotic envelope. Such dynamic…
We characterized the DC transport response of a diode embedded in a THz quantum cascade laser as the laser current was changed. The overall response is described by parallel contributions from the rectification of the laser field due to the non-linearity of the diode I-V and from thermally activated transport. Sudden jumps in the diode response when the laser changes from single mode to multi-mode operation, with no corresponding jumps in output power, suggest that the coupling between the diode and laser field depends on the spatial distribution of internal fields. The results demonstrate con…
It is shown that optical synthesis of terahertz and millimeter-wave frequencies can be achieved using two-mode and mode-locked discrete mode diode lasers. These edge-emitting devices incorporate a spatially varying refractive index profile which is designed according to the spectral output desired of the laser. We first demonstrate a device which supports two primary modes simultaneously with high spectral purity. In this case sinusoidal modulation of the optical intensity at terahertz frequencies can be obtained. Cross saturation of the material gain in quantum well lasers prevents simultaneo…
the realization of high repetition rate passively Q-switched monolithic microlaser is a challenge since a decade. To achieve this goal, we report here on the first passively Q-switched diode-pumped microchip laser based on the association of a Nd:GdVO4 crystal and a Cr4+:YAG saturable absorber. The monolithic design consists of 1 mm long 1% doped Nd:GdVO4 optically contacted on a 0.4 mm long Cr4+:YAG leading to a plano-plano cavity. A repetition rate as high as 85 kHz is achieved. The average output power is approximately 400 mW for 2.2 W of absorbed pump power and the pulse length is 1.1 ns.
A class of multiwavelength Fabry-Perot lasers is introduced where the spectrum is tailored through a non-periodic patterning of the cavity effective index. The cavity geometry is obtained using an inverse scattering approach and can be designed such that the spacing of discrete Fabry-Perot lasing modes is limited only by the bandwidth of the inverted gain medium. A specific two-color semiconductor laser with a mode spacing in the THz regime is designed, and measurements are presented demonstrating the simultaneous oscillation of the two wavelengths. The extension of the Fabry-Perot laser conce…
6-mJ, 4-ns Pulse Generation at 2.09 $μ$m from a Diode-Pumped Ho:YAG Thin-Disk Laser
HiLASE Centre, Institute of Physics of the Czech Academy of Sciences（捷克科学院物理研究所 HiLASE 中心）；Celestia Energy s r.o.（Celestia Energy 有限公司）；CRYTUR, spol. s r.o.（CRYTUR 有限公司）
A semiconductor diode laser having a modified Littrow external resonator is described. An additional output coupling mirror in a V-shape configuration of the resonator makes the system more efficient and convenient to operate.
Random lasers (RLs) are intriguing devices with promising applications as light sources for imaging, sensing, super resolution spectral analysis or complex networks engineering. RLs can be obtained from optically pumped dyes, optical fibers and crystals, or electrically pumped semiconductor heterostructures. Semicon-ductor RLs are usually fabricated by introducing scattering defects into the active layer, adding a degree of complexity to the fabrication process and losing the ease of realization potentially offered by disordered structures. Ready availability of electrically pumped RLs, avoidi…
We characterize a semiconductor external cavity diode laser whose optical feedback is provided by a guided mode resonance filter (GMRF). We focus on the spectral properties. The wavelength of operation falls in the telecom range (1506 nm). The GMRF acting both as a wavelength intracavity filter and feedback mirror allows for a compact laser design. The single-mode operation is verified in a wide range of driving currents. We finely tune the cavity length to adjust the frequency by 14 GHz without mode-hops in agreement with the expected free-spectral range of the resonator $\sim$20 GHz. The com…
Multi-photon microscopy is a powerful tool in biomolecular research. Less complex and more cost effective excitation light sources will make this technique accessible to a broader community. Especially semiconductor diode seeded fiber lasers have proven to be robust, low cost and easy to use. However, their wavelength tuning range is often limited, so only a limited number of fluorophores can be accessed. Therefore, different approaches have been proposed to extend the spectral coverage of these lasers. Recently, we showed that four-wave mixing (FWM) assisted stimulated Raman scattering (SRS) …
