Semiconductor Lasers and Diode-based Light Sources for Biophotonics
Semiconductor lasers are small, reliable, low cost, high-performance and user-friendly optical devices which make them highly suitable for a variety of biomedical applications. This edited book gathers experts in the field to cover the fundamentals and technology advances of semiconductor lasers and diode-based lasers with a focus on their applications in medical optics and biophotonics including edge-emitting semiconductor lasers and light emitting diodes, Q-switched and mode-locked lasers, quantum cascade lasers, semiconductor disk lasers, near-infrared spectroscopy systems for biomedical applications, bio-medical Raman spectroscopy, nonlinear imaging and optical coherence tomography.
Inspec keywords: laser mode locking; quantum cascade lasers; semiconductor lasers; infrared spectroscopy; nanophotonics; optical tomography; optical frequency conversion; surface emitting lasers; laser applications in medicine; Q-switching; Raman spectroscopy; semiconductor device models; biomedical optical imaging; superluminescent diodes; photoluminescence
Other keywords: biomedical applications; semiconductor light sources; bio-medical Raman spectroscopy; diode-laser-induced luminescence; high-power lasers; Q-switched; light-emitting diode technologies; diode-based light sources; near-infrared spectroscopy; biophotonics; optical coherence tomography; figures of merit; nonlinear frequency conversion; edge-emitting semiconductor lasers; diode laser systems; mode-locked lasers; nonlinear imaging; GaN-based blue vertical-cavity surface-emitting lasers; superluminescent light-emitting diodes; semiconductor disk lasers; upconverting nanoparticles; quantum cascade lasers; semiconductor lasers
Subjects: Lasing action in semiconductors; General electrical engineering topics; Laser beam modulation, pulsing and switching; mode locking and tuning; Laser resonators and cavities; Laser resonators and cavities; Semiconductor lasers; Light emitting diodes; Optical harmonic generation, frequency conversion, parametric oscillation and amplification; Patient diagnostic methods and instrumentation; Semiconductor device modelling, equivalent circuits, design and testing; Optical and laser radiation (biomedical imaging/measurement); Nanophotonic devices and technology; Laser beam modulation, pulsing and switching; mode locking and tuning; Optical and laser radiation (medical uses); Design of specific laser systems; Optical harmonic generation, frequency conversion, parametric oscillation and amplification; Nanophotonic devices and technology; Textbooks; IR spectroscopy and spectrometers; Biological and medical applications of lasers
- Book DOI: 10.1049/PBHE007E
- Chapter DOI: 10.1049/PBHE007E
- ISBN: 9781785612725
- e-ISBN: 9781785612732
- Page count: 472
- Format: PDF
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Front Matter
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1 Introduction to semiconductor light sources and their biomedical applications
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The present chapter serves as a brief introduction to semiconductor light sources mainly laser diodes and light emitting diodes, and the basic physical properties of their semiconductor materials. The chapter also discusses the main reasons for semiconductor light sources being attractive for biomedical applications which range from patient diagnostics imaging to direct treatment such as using photodynamic therapy. It is expected that this specific application area will grow significantly in the future, and that it will be an increasingly important physical properties part of the semiconductor industry.
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2 Fundamentals on modeling of edge-emitting semiconductor lasers and superluminescent light-emitting diodes
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The following aspects are modelled: edge-emitting semiconductor lasers; superluminescent light-emitting diodes; semiconductor material electro-optical characteristics; optical gain; spontaneous emission; optical waveguides; transverse optical mode calculation; carrier photon interaction; laser cavities; carrier transport; time domain; buried heterostructure; and quantum dot lasers.
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3 Q-switched and mode-locked lasers for biophotonic applications
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We have attempted an overview of fast-pulsating lasers (gain-switched, Q-switched and mode-locked) in various biomedical applications. By necessity, the accents in the chapter have been to an extent coloured by our research experience and interests; apologies are extended to those authors whose work may have been omitted. Different properties of a laser system are important for different applications (e.g., high instantaneous and average power for multiphoton spectroscopy vs. spectral tuning range for OCT), but all the designs above benefit from the properties of semiconductor lasers such as chip compactness, ease of pumping, and high gain per unit length. The use of nanostructures, particularly QDs, has been shown to open new exciting opportunities.
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4 Light-emitting diode technologies
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LED technology is inherently superior in terms of energy efficiency (with wall plug efficiency exceeding 40%), reliability (lifetime exceeding 50,000 h), robustness and environmental friendliness (involving no hazardous materials). Compared to the CFL which delivers 60 lumens/W of energy consumed, the most advanced white light LEDs are capable of providing over 100 lumens of optical power with the same amount of energy consumed. With further breakthroughs in material epitaxy, chip design, device processing and die packaging, there is plenty of room for boosting energy efficiencies to even higher levels, benefitting not just general lighting but a wide range of scientific applications.
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5 GaN-based blue vertical-cavity surface-emitting lasers
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In this chapter, we provide a brief review of the optical and electrical pumped GaN based vertical-cavity surface-emitting lasers from the fabrication technology to output characteristics analysis. Three types of vertical cavity surface-emitting laser (VCSEL) structures are discussed in the following paragraph including their pros and cons among design and process difficulties. First type is fully epitaxial VCSEL structure, second one is the hybrid microcavity consists of a bottom epitaxial distributed Bragg reflector (DBR) and a top dielectric DBR, and third one is vertical resonator composes dielectric top and bottom DBR. We also present several examples of GaN-based VCSELs achieve laser action under optical and electrical pumping at room temperature.
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6 Quantum cascade lasers
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Quantum cascade lasers (QCLs) and associated devices are compact, room temperature (RT) sources capable of producing electromagnetic radiation in the midinfrared and terahertz (THz) spectral regions. This article will discuss the basic operation of QCLs, the evolution of performance in the past several years, and an overview of material growth and characterization, and QCL device fabrication. This article will also review recent research on mid-infrared QCLs that has resulted in record high wallplug efficiency (WPE), high continuous wave (CW) output power, single mode operation, wide wavelength tunability, and RT THz generation.
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7 Diode laser systems based on nonlinear frequency conversion
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In this chapter, we will give a short introduction to nonlinear frequency conversion with second-order nonlinear optics to provide the basic background to the topic and highlight the important parameters to consider when designing a light source based on frequency conversion. In the following section, the different commonly used implementations of nonlinear frequency conversion will be introduced and some examples of demonstrated laser sources will be given. Finally, we will provide an outlook for the development of frequency converted diode laser light sources and briefly discuss some of the applications.
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8 Semiconductor disk lasers
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Semiconductor disk lasers (SDLs), also known as optically pumped vertical external-cavity surface-emitting lasers (VECSELs), offer unparalleled features combining high beam quality, large wavelength coverage, multi-watt output power, narrow linewidth, and broad tuning range. Moreover, relative to the features they provide, SDLs are compact and cost-effective systems. Their unique properties have already been recognized in biophotonics, for example, in photocoagulation treatment of macular degeneration using yellow radiation and multiphoton imaging, yet their full spread to applications is still to come. This chapter provides an overview of key technology concepts related to SDLs and a summary of the most important developments in terms of wavelength coverage and output powers. Specific developments are presented for SDLs emitting continuous wave (CW) radiation at the yellow-orange-red optical spectrum and for SDLs emitting picosecond pulses at red wavelengths. The chapter is concluded with a review of several biophotonics applications and their needs for laser sources, which are then put in a perspective of current SDL achievements.
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9 Potential biomedical use of diode-laser-induced luminescence from upconverting nanoparticles
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The intention with this chapter is to briefly review the capabilities made possible in the field of biomedical diagnostics and treatment by employing upconverting nanoparticles (UCNPs), as well as the importance of appropriate light sources for such applications. The field of UCNPs in biomedicine has grown rapidly the last decade, since they first were made sufficiently small and bright to be of real interest for biomedical applications. This research has been reviewed previously, while this chapter will focus on recent advances in the use of UCNPs for preclinical applications and diagnostic assays using laser diode excitation.
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10 Near-infrared spectroscopy systems for biomedical applications
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Near infrared spectroscopy in both frequency domain and time domain has many biomedical applications: mainly brain measurements; monitoring tumour chemotherapy responses; diffuse optical spectroscopic tomography imaging; and pulse oximetry.
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11 Semiconductor lasers for bio-medical Raman spectroscopy
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During the 2000's and 2010's Raman spectroscopy has proved its potential to be used for chemical fingerprinting of biological materials. This has enabled this technique to be translated as a novel diagnostic tool for disease diagnosis with high sensitivity and specificity. Raman scattering, being a weak process, relies greatly on the power and spectral quality of the excitation source for its effectiveness. Advent of relatively high power, frequency stabilized semiconductor lasers which has relatively small form factor when compared to its gas laser counterparts enabled developing portable Raman systems for clinical diagnostics.
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12 Nonlinear imaging applications of high-power lasers: figures of merit
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In this chapter, we will perform real time multi-channel confocal microscopy or epi-fluorescence microscopy while performing femtosecond laser induced manipulation, all of these with different laser sources. The different laser systems are compared making use of a figure of merit (FOM) for two-photon interaction and introduce a new FOM for three photon processes. The origin of the FOMs is justified theoretically, becoming a unique tool to select the proper laser system.
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13 Optical coherence tomography
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In this chapter, we will provide a brief explanation of the principle of optical coherence tomography (OCT) imaging and highlight the influence of the light source properties. We will discuss the application of semiconductor lasers in specialized light sources for OCT, namely, in broadband light sources and in broadband wavelength-swept light sources. We will conclude with an outlook on the continuing development of light source technologies for OCT.
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Back Matter
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