Semiconductor Master-Oscillator Power-Amplifiers (MOPAs) are versatile tools for various applications. We will present high-power (P ⪆ 5 W), high-coherence length (Lc ⪆ 100 m), small-sized (L ≤ 25 mm), hybrid semiconductor MOPAs at 920 nm, 976 nm, 1030 nm, 1064 nm, 1120 nm, and 1154 nm. We compare their performance to corresponding distributed Bragg reflector tapered laser and discuss strategies to extend the wavelength range.
In this work, Ridge Waveguide Amplifiers (RWA) with a gain wavelength around 1122nm and different device geometries are analyzed in detail using electro-optical measurements. The measurement results are compared with simulations based on a beam propagation approach to evaluate them and gain a better understanding of the device behavior. Optimized operating conditions are derived with respect to the electro-optical and amplification efficiency of the amplifier. The potential of RWAs with a combination of diffraction-limited beam quality and high output power is demonstrated in miniaturized laser modules supplied with polarization-maintaining optical fibers for input and output and optional nonlinear crystals. More than 200mW of yellow-green laser light with a wavelength of 561nm is provided through the fiber, enabling applications in the bio-medical field.
The impact of optical feedback on the emission properties of edge-emitting diode lasers is crucial for their use in various applications with unavoidable optical feedback. A hybrid master oscillator power amplifier (MOPA) concept based on a low-power laser (MO) and a tapered amplifier (TPA) is well suited for those applications. The MOPA offers the ability to mechanically separate the MO from the TPA, which allows to shield the MO against possible optical feedback from the TPA by using an optical isolator. However, the feedback emitted from the TPA towards the MO has not been investigated in detail yet. In addition to the feedback from the TPA the MOPA as a whole can be subject to external feedback. Depending on the beam path in the respective application, feedback ratios in the range from 10−4 to 10−2 to the TPA may occur. The optical feedback coupled to the TPA is expected to be also amplified in the TPA which increases the feedback towards the MO dramatically. Therefore, the propagation of feedback light through the TPA and its emission characteristics towards the MO have to be studied in detail. A beam propagation method including a model for the charge carriers and a fast thermal solver utilizing a Green’s function approach is used to simulate feedback propagation inside the TPA. A description of the model, with focus on the thermal solver, will be presented as well as a comparison to measurements. The results allow to optimize MOPAs with respect to feedback more accurately.
Tapered diode laser and amplifier structures feature an intrinsic occurrence of different beam waist positions in lateral and vertical direction. The effect, described as astigmatism, shows a changing magnitude in dependence of the device working point. Different working points may therefore require different optical setups to achieve the desired beam shaping and will also affect the overall amplifier setup performance. This work investigates the influences of thermal and charge carrier induced changes to the optical device properties for tapered diode amplifier structures, based on gallium arsenide, at an emission wavelength of λ = 980 nm and a tapered section length of lT P = 4 mm. An advanced beam propagation algorithm was utilized to simulate the optical behavior of the device. To address the dominant influences of localized temperature change and charge carrier distribution the optical model is coupled to a thermal and electrical solver algorithm. General applicable astigmatism mechanisms are described which are based on the insights to the microscopic device functionalities. This includes the influence of different injection current densities, different thermal heat sink conductivities as well as heat spreading on top of the device. The theoretically established outcomes give insight to fundamental tapered amplifier mechanisms, necessary for better understanding of experimental results. Furthermore, the approach opens up the ability to optimize the optical setup which is used to shape the emitted radiation. At the same time limits of the tapered device design will be discussed.
In material processing applications laser diodes are commonly used for pumping of solid-state lasers, providing high efficiencies at demanding optical output powers. Limited by relatively low beam qualities in the high power scheme, their usage in direct material processing applications is still marginal. To achieve power levels in the 30W class, so far the combined radiation of multiple broad area emitters has been necessary. However their output beam quality is far from diffraction limitation and correlated to the aperture width of the emitting laser diode. This work presents a novel miniaturized diode laser module, with an optical output power of more than 30W in continuous wave operation (cw). Simultaneously the output beam is close to the diffraction limit with a beam propagation factor of M2 < 3. The laser module layout is based on tapered diode lasers featuring wavelength stabilization by a monolithic distributed Bragg-grating. The tapered diode laser sources achieve an output power in the order of 8W (cw) at a wavelength around 980 nm. To enhance the output power while maintaining the beam quality of the single emitters, six laser beams were combined by the use of polarization and wavelength coupling. The use of custom designed beam couplers is necessary to combine the given radiation intensities. Therefore a thin film polarizer was adapted to the output wavelength and intensity. Wavelength multiplexing is realized by the use of steep edge filters. By changing the angle of incidence the edge position can be tuned which enables multiple combination steps. All optical components were housed inside of a module with a footprint of 58 x 34mm2 only. The resulting high power and beam quality delivered by the module enables direct material processing.
This work presents a miniaturized laser module featuring an optical output power of more than 14Win continuous wave operation. Simultaneously, a beam quality factor of less than 2 is reached at the operating power. The laser module layout is based on the use of tapered diode lasers featuring wavelength stabilization by a monolithic distributed Bragg grating. Such a single laser source achieves a reliable output power in the order of 8W in continuous wave mode at a wavelength of 980nm [1]. To enhance the output power while maintaining the beam quality of the single emitters, two laser beams were combined by the use of polarization coupling. The use of custom designed beam couplers is necessary to combine the given radiation intensities. A thin film polarization optic, adapted to the output wavelength was used. All optical components where designed to be housed inside of a module with a footprint of 58 x 34mm2. Due to the close spatial vicinity of the laser sources, thermal simulations were carried out to avoid thermal crosstalk and ensure stable laser operation. The modules high beam quality enables pumping of solid state lasers and amplifiers even without challenging optical pumping geometries.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.