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- Samsöe Andersen, Eva, et al.
(författare)
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A novel diode laser system for photodynamic therapy
- 2001
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Ingår i: LASER-TISSUE INTERACTIONS, THERAPEUTIC APPLICATIONS, AND PHOTODYNAMIC THERAPY. - : SPIE. - 0277-786X .- 1996-756X. - 0819441473 ; 4433:33, s. 134-139
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Konferensbidrag (refereegranskat)abstract
- In this paper a novel diode laser system for photodynamic therapy is demonstrated. The system is based on linear spatial filtering and optical phase conjugate feedback from a photorefractive BaTiO3 crystal. The spatial coherence properties of the diode laser are significantly improved. The system provides an almost diffraction limited output which is efficiently coupled into a 50 mum core diameter fiber. The optical power transmitted through the fiber is increased by a factor of six when the feedback is applied to the diode laser. 85 percent of the power from the freely running laser diode is extracted in a high-quality beam and 80 percent of the output power is extracted through the fiber. The power transmitted through tile fiber scales linearly with the power of the laser diode. which means that a laser diode emitting 1.7 W multi-mode radiation would provide 1 W of optical power through a 50 mum core diameter fiber. The system is compact, portable, stable, and easy to operate.
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| 2. |
- Samsöe Andersen, Eva, et al.
(författare)
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Improvement of brightness and output power of high-power laser diodes in the visible spectral region
- 2003
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Ingår i: Optics Communications. - 0030-4018. ; 219:1-6, s. 369-375
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports on a novel design for a high-brightness quantum-well AlGaInP laser-diode system operating at 635 nm. The spatial coherence of two broad area laser diodes is improved using spatial filtering and optical feedback from a narrow mirror stripe on each laser. To increase power, the outputs from the two systems are passively combined using a polarizing beam splitter. The result is a compact system providing a high-brightness beam. The beam-quality parameter is improved in one direction from M-2 = 12 and M-2 = 16 for the two lasers, to M-2 = 2.1 for the combined beam. The other direction of the beam is left unchanged due to its natural high quality with an M-2 value around 1.5. A procedure for efficient coupling of the two lasers into a small core-diameter optical fiber is given. This capability facilitates a wide range of applications including interstitial medical therapies, where delivery of the treatment light through thin optical fibers is essential. (C) 2003 Elsevier Science B.V. All rights reserved.
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| 3. |
- Samsöe Andersen, Eva, et al.
(författare)
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Second-harmonic generation of 405-nm light using periodically poled ${KT}i{OPO}_4$ pumped by external-cavity laser diode with double grating feedback
- 2005
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Ingår i: Applied Physics B. - 0946-2171. ; 80:7, s. 861-864
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Tidskriftsartikel (refereegranskat)abstract
- A frequency-doubled laser diode system for generation of blue-UV light is described. The system is based on an external-cavity high-power laser diode with double feedback from the zeroth and the first orders of a diffraction grating. Light at 405 nm is generated in a single-pass configuration using periodically poled KTiOPO4. We show that the double grating feedback improves the second harmonic conversion efficiency by several orders of magnitude as compared to the freely running laser. The conversion efficiency may be improved further such that higher second-harmonic powers may be generated.
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| 4. |
- Samsöe Andersen, Eva
(författare)
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Laser diode systems for photodynamic therapy and medical diagnostics
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This work concerns techniques for improvement of the coherence properties of diode lasers so that they may be used in two specific medical applications: (Interstitial) photodynamic therapy (PDT) and laser-induced fluorescence diagnostics. In the first application, spatial coherence is crucial, since the treatment light should be delivered through relatively thin optical fibers to optimize treatment and to facilitate minimally invasive treatment. In the second application, a pulsed, blue source at 405nm is desired. This has been approached by frequency doubling the output from an external-cavity laser diode at 810nm. Thus, both spatial and temporal coherence are important to ensure that the second harmonic generation is efficient. Two red (635nm) laser diode systems for PDT, a first and a second generation, have been developed and tested in preliminary clinical trials. The first generation system is based on asymmetrical optical feedback from a barium titanate crystal. This system is coupled into a thin (50µm core diameter) optical fiber and tested in preliminary experimental trials involving interstitial PDT of solid tumors in rat. The second generation system couples two similar systems by means of polarization coupling, whereby the output power is doubled. The individual systems are based on asymmetrical feedback from ordinary mirrors. This system has been tested in PDT treatment of skin cancer in human and has been compared with a conventional treatment. For laser-induced fluorescence diagnostics, an 810nm external-cavity laser diode system with improved spatial and temporal coherence has been constructed. The system is based on a new configuration that employs double feedback from the first diffracted and the zeroth reflected order of a diffraction grating. The output from this system is frequency doubled to 405nm using a single pass configuration with a periodically poled KTP crystal. It has been shown that the double grating feedback improves the second harmonic conversion efficiency by several orders of magnitude as compared with the freely running laser.
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