Tapered Diode Laser Research Articles

Intensity Noise Transfer Through a Diode-Pumped Titanium Sapphire Laser System

In this paper, we investigate the noise performance and transfer in a titanium sapphire (Ti:S) laser system. This system consists of a distributed Bragg-reflector tapered diode laser, which is frequency doubled in two cascaded nonlinear crystals and used to pump the Ti:S laser oscillator. This investigation includes electrical noise characterizations of the utilized power supplies, the optical noise of the fundamental light, the second harmonic light, and finally the optical noise of the femtosecond pulses emitted by the Ti:S laser. Noise features originating from the electric power supply are evident throughout the whole transfer chain. It is demonstrated that improving the electrical noise provides an easy method for reducing the relative intensity noise (RIN) in all stages. The frequency doubled light is shown to have a higher RIN than the fundamental light. In particular, the cascaded system is seen to exhibit higher RIN than a setup with only a single nonlinear crystal. The Ti:S is shown to have a cutoff frequency around 500 kHz, which means that noise structures of the pump laser above this frequency are strongly suppressed. Finally, the majority of the Ti:S noise seems to originate from the laser itself, which partly can be explained by the effect of relaxation oscillation frequency.

Efficient, High Brightness 1030 nm DBR Tapered Diode Lasers With Optimized Lateral Layout

Efficient, high brightness 1030 nm distributed Bragg reflector (DBR) tapered diode lasers with optimized lateral waveguide and grating designs are presented in this paper. The layout changes were carried out in order to enhance the diffraction efficiency of the manufactured DBR gratings and improve the spatial mode filtering for these lasers. In this study, lasers with straight waveguide and grating, straight waveguide and tapered grating, and tapered waveguide and straight grating are compared. The lasers provide an optical output power up to 15.5 W and narrowband emission over the whole power range. Within the studied parameter range, the highest central lobe output power of 10.1 W is obtained for a laser with a tapered grating. The layout comparison also shows that the influence of the applied ridge waveguide injection current density on the central lobe power is significantly different. Here, the lateral design with a tapered grating is the most robust layout. Compared to previous approaches for DBR tapered diode lasers, optimized waveguide and grating designs and their impact on laser performance may help to increase the application potential of such devices.

Reduction of Optical Feedback Originating From Ferroelectric Domains of Periodically Poled Crystals

Optical feedback originating from the interfaces of the periodically poled domains of a nonlinear crystal is usually blocked by a bulky optical isolator to avoid an influence on the pump source. Here, a nonlinear bulk crystal with a slanted design of the periodic poling is used to suppress the optical feedback toward the laser source. This crystal is compared with a conventionally poled crystal, in which the incident radiation propagates perpendicular to the domains. Both crystals are made of magnesium oxide doped congruent lithium niobate (PPMgO:CLN). A distributed Bragg reflector tapered diode lasers with a maximum optical power of 7.0 W at a wavelength of 1122 nm and each nonlinear crystal are employed in a single-pass setup. In comparison with the conventional crystal, the optical feedback of the crystal with slanted domains is reduced by 13.4 dB enabling a stable narrow-band operation of the pump laser source without an optical isolator. The impact of the optical feedback on the diode laser with respect to the optical output power and the spectral behavior is investigated. For the crystal with slanted domains, a frequency doubled output power up to 0.39 W at 561 nm is generated without reaching the coherence collapse regime, as observed in case of the conventional crystal. These results are promising for miniaturization of the setup without a need for a bulky optical isolator.

Coherent laser phase retrieval in the presence of measurement imperfections and incoherent light.

Phase retrieval is a powerful numerical method that can be used to determine the wavefront of laser beams based only on intensity measurements, without the use of expensive, low-resolution specialized wavefront sensors such as Shack-Hartmann sensors. However, phase retrieval techniques generally suffer from poor convergence and fidelity when the input measurements contain electronic or optical noise and/or an incoherent intensity contribution overlapped with the otherwise spatially coherent laser beam. Here, we present an implementation of a modified version of the standard multiple-plane Gerchberg-Saxton algorithm and demonstrate that it is highly successful at extracting the intensity profile and wavefront of the spatially coherent part of the light from various lasers, including tapered laser diodes, at a very high fidelity despite the presence of incoherent light and noise.

Generation of sub-50fs soliton pulses from a mode-locked Yb,Na:CNGG disordered crystal laser.

We experimentally demonstrated a diode-pumped sub-50 fs Yb,Na:CNGG disordered crystal laser. Pumped by a 980 nm distributed Bragg-reflector tapered diode laser and passively mode-locked with a semiconductor saturable absorber mirror (SESAM), soliton pulses as short as 62 fs and 45 fs were obtained without and with external compression, respectively. The ultrashort pulses had a repetition rate of ~104 MHz at the central wavelength of 1061 nm. To the best of our knowledge, this is the first demonstration of sub-50 fs pulses from the Yb3+-doped CNGG type disordered crystal lasers.

Direct Modulation Capabilities of Micro-Integrated Laser Sources in the Yellow–Green Spectral Range

In this letter, the millisecond modulation capabilities of high power multisection diode laser systems and their application to second harmonic generation (SHG) are investigated. Different modulation methods of the optical output power of a distributed Bragg-reflector tapered diode laser and a master oscillator power amplifier (MOPA), both emitting at 1120 nm, are compared. The modulated optical output power features a rectangular pulse shape with pulse lengths in the low millisecond regime and peak optical power above 5 W. Based on these results, the most suitable method for the modulation of the second harmonic emission is identified and applied to micro-integrated modules with an MOPA pump source and different crystals for SHG. At an emission wavelength of 560 nm, rectangular millisecond pulses with a peak power of more than 245 mW are achieved.

Theoretical approach of a polymer stabilized blue phase beam steering

Nematic liquid crystal (LC)-based beam steering has been reported for wide applications. However, for conventional nematic LC beam steering the thickness is of several microns in order to have a wider deflection angle. The response time is relatively slow and the diffraction efficiency is low. In this work, novel beam steering based on polymer stabilized blue phase liquid crystal (PS-BPLC) has been designed and theoretically analyzed. This special mesophase of the chiral doped nematic LC has several advantageous characteristics, for example no need for alignment layers, microsecond response time and an isotropic voltage-off state. The results reveal control over phase retardation. The direction of the steered beam can be tuned by voltage. Depending on voltage configuration, either diffractive beam steering (0.5deg deviation for 1st order) or a tunable continuous phase (tunable deviation of 0.002deg) can be obtained. In the first case, the deflection angle could be tuned by stacks of samples. The second option has the same phase shift for the TE and TM modes so unpolarized light could be used. Full Text: PDF ReferencesF. Feng, I. White, T. Wilkinson, "Free Space Communications With Beam Steering a Two-Electrode Tapered Laser Diode Using Liquid-Crystal SLM", J. Lightwave Technol. 31, 2001 (2013). CrossRef E. Oton, J. Perez-Fernandez, D. Lopez-Molina, X. Quintana, J.M. Oton, M.A. Geday, "Reliability of Liquid Crystals in Space Photonics", IEEE Photonics Journal 7, 1 (2015). CrossRef J. Stockley, S. Serati, "Multi-access laser terminal using liquid crystal beam steering", IEEE in Aerospace Conference, 1972 (2005). CrossRef D. Zografopoulos and E. Kriezis, "Switchable beam steering with zenithal bistable liquid-crystal blazed gratings", Opt. Lett. 39, 5842 (2014). CrossRef Benedikt Scherger, et al., "Discrete Terahertz Beam Steering with an Electrically Controlled Liquid Crystal Device", J. Infrared. Millim. Terahertz Waves 33, 1117 (2012). CrossRef M.A. Geday, X. Quintana, E. Otón, B. Cerrolaza, D. Lopez, F. Garcia de Quiro, I. Manolis, A. Short, Proc. ICSO, Rhodes, Greece, pp. 1-4 (2010). CrossRef Y. Chen, S.-T. Wu, "The outlook for blue-phase LCDs", Proc. SPIE 9005, Advances in Display Technologies IV, 900508 (2014). CrossRef G.D. Love, A.F. Naumov, "Modal liquid crystal lenses", Liq. Cryst. Today 10, 1 (2000). CrossRef V. Urruchi, J.F. Algorri, J.M. Sánchez-Pena, M.A. Geday, X. Quintana, N. Bennis, "Lenticular Arrays Based on Liquid Crystals", Opto-Electron. Rev. 20, 38 (2012). CrossRef J.F. Algorri, G. Love, and V. Urruchi, "Modal liquid crystal array of optical elements", Opt. Express 21, 24809 (2013). CrossRef J.F. Algorri, V. Urruchi, N. Bennis, J. Sánchez-Pena, "Modal liquid crystal microaxicon array", Opt. Lett. 39, 3476 (2014). CrossRef J.F. Algorri, V. Urruchi, B. Garcia-Camara, J.M. Sánchez-Pena, "Generation of Optical Vortices by an Ideal Liquid Crystal Spiral Phase Plate", IEEE Elect. Dev. Lett. 35, 856 (2014). CrossRef D. Xu, Y. Chen, Y. Liu, S. Wu, "Refraction effect in an in-plane-switching blue phase liquid crystal cell", Opt. Express 21, 24721 (2013). CrossRef Z. Ge, S. Gauza, M. Jiao, H. Xianyu, S.T. Wu, "Electro-optics of polymer-stabilized blue phase liquid crystal displays", Appl. Phys. Lett. 94 101104 (2009). CrossRef J. Yan et al., "Extended Kerr effect of polymer-stabilized blue-phase liquid crystals", Appl. Phys. Lett. 96, 071105 (2010). CrossRef X. Wang, D. Wilson, R. Muller, P. Maker, D. Psaltis, "Liquid-crystal blazed-grating beam deflector, Appl. Opt. 39, 6545 (2000). CrossRef

Efficient generation of 3.5 W laser light at 515 nm by frequency doubling a single-frequency high power DBR tapered diode laser

More than 3.5W of green light at 515nm is generated by frequency doubling a single-frequency high power DBR tapered diode laser. The frequency doubling is performed in a cascade of PPMgLN and PPMgSLT crystals in order to reach high power and avoid thermal effects present in PPMgLN at high power. The green light is diffraction limited (M2 <1.1) and single-frequency operation is demonstrated with a linewidth less than 2pm.

Highly efficient multimode diode-pumped Yb:KYW laser

Record high differential efficiency (53.2%) and full optical efficiency (48%) for a multimode diode-pumped Yb:KYW laser have been achieved. The characteristics of the laser and methods for improving its efficiency using a distributed Bragg reflector tapered diode laser (DBR TDL) are discussed.

Efficient generation of 1.9 W yellow light by cascaded frequency doubling of a distributed Bragg reflector tapered diode.

Watt-level yellow emitting lasers are interesting for medical applications, due to their high hemoglobin absorption, and for efficient detection of certain fluorophores. In this paper, we demonstrate a compact and robust diode-based laser system in the yellow spectral range. The system generates 1.9 W of single-frequency light at 562.4 nm by cascaded single-pass frequency doubling of the 1124.8 nm emission from a distributed Bragg reflector (DBR) tapered laser diode. The absence of a free-space cavity makes the system stable over a base-plate temperature range of 30 K. At the same time, the use of a laser diode enables the modulation of the pump wavelength by controlling the drive current. This is utilized to achieve a power modulation depth above 90% for the second harmonic light, with a rise time below 40 μs.

Injection Current-Dependent Single-Mode Fiber Coupling of a DBR Tapered Diode Laser Beam

In this letter, we investigate experimentally the influence of injection current-induced beam astigmatism change in a distributed Bragg reflector tapered diode laser on launching of its nearly diffraction limited, simple astigmatic laser beam into a single-mode fiber (SMF). In particular, the optical power and the laser beam properties in front and behind the SMF are examined in dependence on the current injected into the taper section of the diode laser. The fiber coupling measurements are conducted at two fixed configurations of the applied optical system, each of which is optimized for a different taper current value. A maximum power of 3.5 W ex SMF at a coupling efficiency of 67% is reached.

DBR tapered diode laser with 12.7 W output power and nearly diffraction-limited, narrowband emission at 1030 nm

A 1030 nm distributed Bragg reflector (DBR) tapered diode laser with nearly diffraction-limited emission is presented. The laser provides an optical output power of 12.7 W with an electro-optical efficiency >40 %. At 10.5 W of optical output power, a central lobe power content of 8.1 W and a nearly diffraction-limited beam propagation ratio of M2 = 1.1 (1/e2) are obtained. The corresponding brightness is 700 MW cm−2 sr−1. Compared to previous approaches, intrinsic wavelength stabilization is obtained by a third-order DBR grating manufactured using more reproducible electron-beam lithography. A narrowband emission is measured over the whole power range with a spectral bandwidth of about 17 pm at 12.5 W. Based on the measured electro-optical, spectral and spatial properties, the laser is suitable for applications requiring narrowband, high-power emission with high spatial quality.

Watt-level second-harmonic generation at 589 nm with a PPMgO:LN ridge waveguide crystal pumped by a DBR tapered diode laser.

A DBR tapered diode laser in continuous wave operation was used to generate second-harmonic radiation at 589 nm in a PPMgO:LN ridge waveguide crystal. An optical output power of 0.86 W at an optical-to-optical and an electrical-to-optical efficiency of 42% and 11%, respectively, was achieved. The visible radiation was characterized by a spectral bandwidth ΔνFWHM of 230 MHz and a beam propagation parameter M1/e22 better than 1.1. The integration of such a system into a housing of a small footprint will enable a portable and highly efficient module featuring a visible output power in the watt-level range.

Rear-side resonator architecture for the passive coherent combining of high-brightness laser diodes.

We describe a new coherent beam combining architecture based on passive phase locking of emitters in an extended cavity on the rear facet and their coherent combination on the front facet. This rear-side technique provides strong optical feedback for phase locking while maintaining a high electrical-to-optical efficiency. Two high-brightness high-power tapered laser diodes are coherently combined using a Michelson-based cavity. The combining efficiency is above 82% and results in an output power of 6.7 W in a nearly diffraction-limited beam with an M(4σ)(2)≤1.2. A semi-active automatic adjustment of the current enhances the long-term stability of the combination, while the short-term stability is passively ensured by the extended cavity. This new laser configuration exhibits the simplicity of passive self-organizing architectures while providing a power conversion efficiency of 27% that is comparable to master oscillator power amplifier architectures.

高亮度锥形半导体激光器

高亮度锥形半导体激光器

Multiphoton imaging with a novel compact diode‐pumped Ti:sapphire oscillator

Multiphoton laser scanning microscopy commonly relies on bulky and expensive femtosecond lasers. We integrated a novel minimal-footprint Ti:sapphire oscillator, pumped by a frequency-doubled distributed Bragg reflector tapered diode laser, into a clinical multiphoton tomograph and evaluated its imaging capability using different biological samples, i.e. cell monolayers, corneal tissue, and human skin. With the novel laser, the realization of very compact Ti:sapphire-based systems for high-quality multiphoton imaging at a significantly size and weight compared to current systems will become possible.

Concept for power scaling second harmonic generation using a cascade of nonlinear crystals.

Within the field of high-power second harmonic generation (SHG), power scaling is often hindered by adverse crystal effects such as thermal dephasing arising from the second harmonic (SH) light, which imposes limits on the power that can be generated in many crystals. Here we demonstrate a concept for efficient power scaling of single-pass SHG beyond such limits using a cascade of nonlinear crystals, in which the first crystal is chosen for high nonlinear efficiency and the subsequent crystal(s) are chosen for power handling ability. Using this highly efficient single-pass concept, we generate 3.7 W of continuous-wave diffraction-limited (M(2)=1.25) light at 532 nm from 9.5 W of non-diffraction-limited (M(2)=7.7) light from a tapered laser diode, while avoiding significant thermal effects. Besides constituting the highest SH power yet achieved using a laser diode, this demonstrates that the concept successfully combines the high efficiency of the first stage with the good power handling properties of the subsequent stages. The concept is generally applicable and can be expanded with more stages to obtain even higher efficiency, and extends also to other combinations of nonlinear media suitable for other wavelengths.

High-power diode lasers at 1178 nm with high beam quality and narrow spectra.

High-power distributed Bragg reflector tapered diode lasers (DBR-TPLs) at 1180nm were developed based on highly strained InGaAs quantum wells. The lasers emit a nearly diffraction-limited beam with more than two watts with a narrow spectral width. These features are believed to make this type of diode laser a key component for the manufacturing of miniaturized laser modules in the yellow and orange spectral range by second-harmonic generation to cover a spectral region currently not accessible with direct emitting diode lasers. Future applications might be the laser-cooling of sodium, high-resolution glucose-content measurements, as well as spectroscopy on rare earth elements.

Efficient generation of 509 nm light by sum-frequency mixing between two tapered diode lasers

We demonstrate a concept for visible laser sources based on sum-frequency generation of beam combined tapered diode lasers. In this specific case, a 1.7W sum-frequency generated green laser at 509nm is obtained, by frequency adding of 6.17W from a 978nm tapered diode laser with 8.06W from a 1063nm tapered diode laser, inside a periodically poled MgO doped lithium niobate crystal. This corresponds to an optical to optical conversion efficiency of 12.1%. As an example of potential applications, the generated nearly diffraction-limited green light is used for pumping a Ti:sapphire laser, thus demonstrating good beam quality and power stability. The maximum output powers achieved when pumping the Ti:sapphire laser are 226mW (CW) and 185mW (mode-locked) at 1.7W green pump power. The optical spectrum emitted by the mode-locked Ti:sapphire laser shows a spectral width of about 54nm (FWHM), indicating less than 20fs pulse width.

Compact Blue Light Source by Single-Pass Second Harmonic Generation of DBR Tapered Laser Radiation

We demonstrate a continuous-wave 460-nm compact visible laser module having a footprint of 75 mm × 25 mm × 25 mm. This blue light source is achieved through single-pass second harmonic generation with a distributed Bragg reflector tapered diode laser as a single-frequency pump source at ~920 nm in a periodically poled MgO-doped lithium niobate crystal with a planar waveguide. The compact blue laser module reached an optical output power of 286 mW with the highest optical conversion efficiency of 11.6% at room temperature. The power stability of the blue light from the laser module is measured at an output power of 268 mW with a variation of ±3.5% during a period of 1 h.