Single-mode and single-beam surface emission from visible red GaInP/AlGaInP laser diodes

Kellermann, P.O.; Golshani, A.; Köck, A.; Gornik, E.; Gauggel, H.-P.; Winterhoff, R.; Pilkuhn, M. H.

doi:10.1063/1.118877

Cited by 9 publications

(2 citation statements)

References 20 publications

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“…At 675.2 nm, near the film's absorption maximum, a dose gradient in the radiation field leads to a change in optical density that is up to three times larger than the change that is caused by the same dose gradient in the valley (632.8 nm) of the film's absorption spectrum. The GaInP/AlGaInP-laser diode used is a single-mode emitting device with two beams of edge emission and one top-surface beam in the direction of 32.5 • to the active layer, which is achieved by applying the surface mode emission technique (Kellermann et al 1997). The laser light propagating in the active region excites a transverse electrically polarized (TE 0 ) surface mode in the waveguide structure on the top of the laser diode through grating coupling.…”

Section: Densitometry Systemmentioning

confidence: 99%

A new method of readout in radiochromic film dosimetry

1998

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Radiochromic film as a dosimetry medium offers several advantages in high-resolution radiography. A new technique of readout was developed to measure the optical density distributions of the film in purely directed light. This technique implements radiochromic film dosimetry near the film's absorption maximum by using a single-mode top-surface emitting laser diode (675.2 nm). The effective sensitivity of the film, compared with a helium-neon laser densitometer (632.8 nm), is increased approximately threefold. Good accuracy, high spatial resolution and simple assembly of the readout system is achieved. Beam profiles of the four final collimator helmets of a Leksell Gamma Knife (Elekta Inc., Sweden) were experimentally determined. Measured profiles and full-widths at half maximum are consistent with the computer generated data of the dose planning system (Kula 4.4, Elekta Inc., Sweden). The output factor of the 4 mm collimator (the smallest collimator with the steepest dose gradient), essential for the application of well defined doses, was checked. The measurements established an output factor of 826 +/- 9 that lies 9 +/- 1% lower than the adjusted one.

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Section: Densitometry Systemmentioning

confidence: 99%

A new method of readout in radiochromic film dosimetry

1998

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“…17,18 The radiation and the longitudinal-mode characteristics of the waveguide-grating structures have been investigated numerically with an in-depth analysis based on the Floquet-Bloch theory. 19 The numerical analysis shows that in the case of contradirectional coupling the resonance is more than five times narrower than in the case of the codirectional coupling mechanism.…”

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confidence: 99%

Wavelength-adjustable surface-emitting single-mode laser diodes with contradirectional surface-mode coupling

Kellermann

Finger

Schrenk

et al. 1999

Applied Physics Letters

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Single-mode surface emission has been achieved from visible red GaInP/AlGaInP laser diodes by applying the contradirectional surface-mode coupling technique. The emission wavelength (679.4 nm) of the laser structures was adjusted (decreased) in steps of 0.2 nm in an interval of 1.2 nm by reducing the thickness of the waveguide on top of the laser diode. The laser diodes emitted via the surface with a beam divergence of 0.12° and showed single-mode emission both in ac as well as in dc operation with a minimum spectral linewidth of 0.09 nm. The highest side-mode suppression achieved in dc operation was 26 dB.

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