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Design and fabrication of GaN-based laser diodes for single-mode and narrow-linewidth applications

2013-12-11 Science
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Release : 2013-12-11
Genre : Science
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Book Rating : 868/5 ( reviews)

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Book Synopsis Design and fabrication of GaN-based laser diodes for single-mode and narrow-linewidth applications by : Luca Redaelli

Download or read book Design and fabrication of GaN-based laser diodes for single-mode and narrow-linewidth applications written by Luca Redaelli. This book was released on 2013-12-11. Available in PDF, EPUB and Kindle. Book excerpt: In this work, several aspects concerning (In,Al,Ga)N laser diodes with high spectral purity, designed for applications in spectroscopy, were studied. A complete fabrication process for ridgewaveguide laser diodes on GaN substrate was developed. The lateral size of the ridge waveguides was as narrow as 1.5 μm: this is necessary in order to achieve lateral single-mode lasing in (In,Al,Ga)N laser diodes. A peculiar property of (In,Al,Ga)N laser diodes is that, when the ridge is narrow, the threshold current strongly depends on the ridge etch depth. This phenomenon was investigated by fabricating laser diodes with different etch depths. For ridge widths below 2 μm, the threshold current of shallow-ridge devices was found to be more than two times larger than that of comparable deep-ridge devices. Moreover, in the lateral far-field patterns of shallow-ridge laser diodes, side-lobes were observed, which would support the hypothesis of strong index-antiguiding. The antiguiding factor at threshold was experimentally determined to be about 10, which is among the largest values ever published for (In,Al,Ga)N laser diodes. The devices were further studied by simulation, and the results confirmed that the carrier-induced index change in the quantum wells can compensate the lateral index step if the ridge is shallow. This, in turn, reduces the lateral optical confi nement, which increases the threshold current and generates side lobes in the far-fi eld patterns. Based on this research, blue and violet laser diodes suitable for packaging in TO cans and continuous-wave (CW) operation exceeding 50 mW were fabricated. An external cavity diode laser (ECDL) was also realized, which could be tuned over the spectral range 435 nm - 444 nm and provided a peak emission power of more than 27 mW CW at 439 nm. As an alternative approach to obtain a narrow spectral linewidth, the feasibility of monolithically integrated Bragg-gratings was studied.

Design and Fabrication of GaN Based Laser Diodes for Single Mode and Narrow Linewidth Aplications

2013
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Release : 2013
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Book Synopsis Design and Fabrication of GaN Based Laser Diodes for Single Mode and Narrow Linewidth Aplications by : Luca Redaelli

Download or read book Design and Fabrication of GaN Based Laser Diodes for Single Mode and Narrow Linewidth Aplications written by Luca Redaelli. This book was released on 2013. Available in PDF, EPUB and Kindle. Book excerpt:

A deep ultraviolet laser light source by frequency doubling of GaN based external cavity diode laser radiation

2022-05-13 Technology & Engineering
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Release : 2022-05-13
Genre : Technology & Engineering
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Book Rating : 13X/5 ( reviews)

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Book Synopsis A deep ultraviolet laser light source by frequency doubling of GaN based external cavity diode laser radiation by : Norman Ruhnke

Download or read book A deep ultraviolet laser light source by frequency doubling of GaN based external cavity diode laser radiation written by Norman Ruhnke. This book was released on 2022-05-13. Available in PDF, EPUB and Kindle. Book excerpt: A compact and portable laser light source emitting in the wavelength range between 210 nm and 230 nm would enable numerous applications outside of laboratory environments, such as sterilization and disinfection of medical equipment, water purification or gas and air analysis using absorption spectroscopy. Such a source is also highly attractive for the identification and quantification of proteins and biomolecules by means of laser-induced fluorescence or Raman spectroscopy. In this thesis, a novel concept to realize such a compact and portable laser light source with low power consumption and an emission around 222 nm is investigated. The developed concept is based on single-pass frequency doubling of a commercially available high-power GaN laser diode emitting in the blue spectral range. Due to the low frequency doubling conversion efficiencies in this wavelength range of about 10-4 W-1, a laser diode with high optical output power above 1 W is required as pump source. Moreover, it has to exhibit narrowband emission in the range of the acceptance bandwidth of the applied nonlinear BBO crystal. Since GaN-based high-power laser diodes typically show broad emission spectra of Δλ = 1…2 nm, stabilizing and narrowing their wavelength by using external wavelength-selective elements is investigated and presented for the first time. With the understanding for the novel concept gained in this work, a compact ultraviolet laser light source was realized. It has a power consumption of less than 10 W and is exceptionally robust due to its immoveable components. The demonstrated output power of 160 μW enables numerous industrial and everyday applications for which previous laser systems have been too complex and overly cost- and energy-intensive.

Epitaxial Design Optimizations for Increased Efficiency in GaAs-Based High Power Diode Lasers

2021-04-09 Science
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Release : 2021-04-09
Genre : Science
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Book Rating : 963/5 ( reviews)

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Book Synopsis Epitaxial Design Optimizations for Increased Efficiency in GaAs-Based High Power Diode Lasers by : Thorben Kaul

Download or read book Epitaxial Design Optimizations for Increased Efficiency in GaAs-Based High Power Diode Lasers written by Thorben Kaul. This book was released on 2021-04-09. Available in PDF, EPUB and Kindle. Book excerpt: This work presents progress in the root-cause analysis of power saturation mechanisms in continuous wave (CW) driven GaAs-based high-power broad area diode lasers operated at 935 nm. Target is to increase efficiency at high optical CW powers by epitaxial design. The novel extreme triple asymmetric (ETAS) design was developed and patented within this work to equip diode lasers that use an extremely thin p-waveguide with a high modal gain. An iterative variation of diode lasers employing ETAS designs was used to experimentally clarify the impact of modal gain on the temperature dependence of internal differential quantum efficiency (IDQE) and optical loss. High modal gain leads to increased free carrier absorption from the active region. However, less power saturation is observed, which must then be attributed to an improved temperature sensitivity of the IDQE. The effect of longitudinal spatial hole burning (LSHB) leads to above average non-linear carrier loss at the back facet of the device. At high CW currents the junction temperature rises. Therefore, not only the asymmetry of the carrier profile increases but also the average carrier density in order to compensate for the decreased material gain and increased threshold gain. This carrier non-pinning effect above threshold is found in this work to enhance the impact of LSHB already at low currents, leading to rapid degradation of IDQE with temperature. This finding puts LSHB into a new context for CW-driven devices as it emphasizes the importance of low carrier densities at threshold. The carrier density was effectively reduced by applying the novel ETAS design. This enabled diode lasers to be realized that show minimized degradation of IDQE with temperature and therefore improved performance in CW operation.

Two-step MOVPE, in-situ etching and buried implantation: applications to the realization of GaAs laser diodes

2021-03-25 Science
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Release : 2021-03-25
Genre : Science
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Book Rating : 971/5 ( reviews)

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Book Synopsis Two-step MOVPE, in-situ etching and buried implantation: applications to the realization of GaAs laser diodes by : Pietro della Casa

Download or read book Two-step MOVPE, in-situ etching and buried implantation: applications to the realization of GaAs laser diodes written by Pietro della Casa. This book was released on 2021-03-25. Available in PDF, EPUB and Kindle. Book excerpt: This work is about two-step epitaxial growth using metalorganic vapor-phase epitaxy (MOVPE) for the realization of edge-emitting near-infrared laser diodes. The fabricated gallium arsenide-based devices fall into two categories: high-power lasers (watt range, multimodal) and tunable lasers (milliwatt range, monomodal). Common to both cases is that surface contamination – particularly that due to oxygen – needs to be removed before regrowth. Thus, in-situ etching with carbon tetrabromide (CBr4) is first studied. The experimental results include kinetic data, the effects of different etching conditions as well as substrate characteristics, and the effectiveness in reducing surface contamination. These investigations pave the way to devices based on 2-step epitaxy combined with in-situ etching. Correspondingly, thermally-tuned SG-DBR lasers operating around 975 nm have been successfully realized, obtaining a tuning range of 21 nm. In addition, the possibility of using electronic tuning in similar devices has been explored. High-power broad-area lasers have also been realized, using two-step epitaxy combined with ex-situ and in-situ etching, to create a buried, shallow “mesa” containing the active zone. This approach allows introducing lateral electrical and optical confinement, and – simultaneously – non-absorbing mirrors at the laser facets. Additionally, a different strategy to create a buried current aperture is presented, which is based on ion implantation followed by epitaxial regrowth. This enables to improve device performance and simultaneously introduce non-absorbing mirrors at the facets with correspondingly increased reliability.

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