Near-field and far-field dynamics of (Al,In)GaN laser diodes

Abstract

Near- and far-field dynamics of edge-emitting (Al,In)GaN laser diodes are measured simultaneously with a 100 nm spatial and a 5 ns temporal resolution using a scanning near-field microscope. We reconstruct the phase distribution at the laser diode facet. Beam steering and near-field mode dynamics are interpreted in terms of thermal and carrier induced change of refractive index in the waveguide.

High power broad ridge (Al,In)GaN laser diodes: Spatial and spectral stability

“…For the near-field measurement the intensity distribution at the front facet of the LD is projected onto a CCD chip or a single mode optical fiber, located in the focal plane of an imaging setup. In [7] this experimental method is discussed in detail and compared to scanning near-field optical microscopy (SNOM), which can be used for similar measurements [8]. The imaging setup is an Gaussian telescope, which is, in principle, a combination of an aspheric To improve the output power of (Al,In)GaN laser diodes (LDs), the ridge width has to be increased, but beam quality of GaN-based broad area lasers is still a critical point.…”

Spectrally resolved confocal microscopy for laser mode imaging and beam characteristic investigations

“…Similar investigations have been performed above the laser threshold utilizing SNOM on an EEL by Schwarz et al 7 However without a monochromator for high spectral resolution, the setup from U.T. In the regime close to the laser threshold, the still coherent intensity patterns are measured and compared to simulations.…”

“…For example, high spatially resolved images of laser device emission can be used to characterize the laser modes, 1,2 to determine the beam profile of a laser 3 and can also be used to get information about the internal structure of a laser device. 7,8 Furthermore, spectrally resolved SNOM was also applied on vertical cavity surface emitting lasers ͑VCSEL͒ ͑Refs. 5 The most prominent characterization method for optical measurements in the nm regime is scanning near field optical microscopy ͑SNOM, or NSOM͒.…”

Optical Properties of Edge‐Emitting Lasers: Measurement and Simulation

“…The evanescent tail of the mode in the active laser waveguide can excite a resonant mode in the substrate, depending on its amplitude at the cladding-substrate interface and frequency. The laser diode has been driven in a pulsed mode, and details of the measurement can be found in [7,8]. The propagation vector of the mode is then tilted towards the substrate.…”