ISBN 9783843955607

978-3-8439-5560-7, Reihe Physik

Lena Engel
Control of the far field of classical and non-classical light sources

313 Seiten, Dissertation Universität Stuttgart (2024), Softcover, A5

Zusammenfassung / Abstract

For classical as well as for quantum photonics, high-quality light sources, offering a well-defined far field in combination with a high extraction efficiency, are required in various fields of application.

The semiconductor vertical-surface emitting lasers (VCSELs) are integrated in a broad range of utilization as they offer several benefits like low threshold current and a circular beam profile. Explicitly VCSELs in the red-spectral range are appealing for employment in medical technologies and sensing. The main challenges are the divergence and the trade-off between high output power and a Gaussian-shape of the far field.

For the realization of quantum photonics, high quality sources, emitting single photons on demand, are required. Semiconductor quantum dots (QDs) have proven to be auspicious candidates here, offering the emission of single photons with high purity. Due to their epitaxial growth, they are embedded in a semiconductor matrix, strongly limiting the extraction efficiency.

This thesis aims for the control of the far field of red-emitting VCSELs as well as semiconductor QDs. In order to collimate the VCSEL's emission, polymer microlenses are integrated on-chip. To control the modal characteristics, surface reliefs are integrated. Polymer microlenses are combined with the surface reliefs for the first time in the context of red-emitting VCSELs. This enables the full control over the far field and thus highly collimated fundamental-mode emission across the entire operation range.

For enhanced extraction efficiency of QDs, two approaches are presented. First, wet-chemically etched Gaussian-shaped microlenses for the geometric broadband enhancement of the collection efficiency in the telecom C-band are investigated. Second, Gaussian-shaped microcavities for Purcell-enhanced single-photon emission are introduced, realized by monolithic overgrowth in the near-infrared regime and by a hybrid approach to reach the telecom C-band.