We study coherent laser arrays operating in epitaxially grown semiconductor membrane quantum wells. The samples are deposited by transfer on substrates of oxidized silicon and we record the real and reciprocal space of the laser emission. The Laser arrays are in a lateral emission geometry and are waveguides lasers where the end mirrors are the end-facets of the cleaved membranes which usually form cavities in the order of 100 microns. We are able to create waveguide laser arrays with modal widths of approximately 5-10 microns separated by 10-20 microns. We use real and reciprocal space imaging to examine the emission characteristics of the lasing cavity. Remarkably, we discover that the mutual coherence is preserved whether the cavity operates on a single longitudinal mode or multiple modes. We will show how their emission and coherence can be controlled using a digital micromirror device to control the position and shape of the pump illumination studying threshold, coherence and frequency.
We present coherent laser arrays in a silicon photonics compatible waveguide geometry in optically pumped semiconductor membrane quantum well lasers (MQWLs) on oxidised silicon and silicon carbide substrates. Real and reciprocal space imaging is used to investigate the emission of the laser arrays and mutual coherence is seen to be maintained while operating on single and multiple longitudinal modes in each cavity. Further, we investigate writing laser cavity arrays through micro-structuring of the MQWL and also through the utilisation of a spatial light modulator (SLM) to define areas of gain in the MQWL by shaping the pump beam.
We present continuous wave bi-frequency operation in an optically pumped membrane external-cavity surface-emitting laser (MECSEL). A laser ablation system utilising a digital micromirror device is used to define areas of intra-cavity loss by removing Bragg layers from the surface of the cavity mirror in a crosshair pattern with an undamaged central area. Our MECSEL simultaneously operates on two Hermite-Gaussian spatial modes, the fundamental and a higher order mode, by aligning the laser cavity to be centred on a masked area. We demonstrate bi-frequency operation with a wavelength separation on the order of 5 nm around 1005 nm.
This conference presentation was prepared for the Quantum Technology: Driving Commercialisation of an Enabling Science III conference at SPIE Photonex, 2022.
Optically pumped waveguide coherent laser arrays are demonstrated in an 1-micron-thick-semiconductor-membrane-InGaAs-quantum-well laser transferred on a silicon carbide heat spreader emitting at 1010 nm. We employ a real and Fourier space imaging setup to study the emission of single and arrays of laser cavities. We are able to create waveguide laser arrays with modal widths of approximately 5-10 μm separated by 5-10 μm which maintain their mutual coherence while operating on either single or multiple longitudinal modes. This laser geometry can be accurately controlled by the laser pump and they offer a new high gain laser platform that permits integration with photonic structures.
There is significant interest in developing laser wavelengths between 700 and 800 nm that may then be frequency doubled to the UV for applications in spectroscopy and atomic physics. We present our most recent results on both a 739 nm AlGaAs/AlGaInP VECSEL, where we demonstrate 150 mW of CW power suitable for frequency doubling to the Yb+ cooling transition at 369.5 nm, and a 780nm AlGaAs/AlGaInP VECSEL which was utilised in a novel demonstration of second harmonic generation in a Zinc-indiffused MgO:PPLN waveguide. In the latter we have generated 1 mW of power at 390 nm.
We show the characterisation of spectral broadening in the Tantalum Pentoxide waveguide system as a function of pump wavelength, showing spectra for central pump wavelengths of 0.9 to 1.5 um (150 fs, 80 MHz). We have achieved octave spanning spectra with approximately 5 mW of laser power coupled in the waveguide at 1 um pumping wavelength for a linear buried waveguide using a commercial source.
Dual frequency comb generation is a field which has seen considerable interest in recent years, with notable implementations such as dual wavelength operation of a Mode-locked Integrated External-cavity Surface Emit- ting Laser (MIXSEL), CW pumping of orthogonal polarisation states in a microring resonator, and optical phase-locking of discrete frequency combs. Dual frequency operation of CW Vertical External Cavity Surface Emitting Lasers (VECSEL) has been demonstrated in a particularly well controlled way using sub-wavelength metallic masks fabricated onto the surface of the laser gain structure. We present a variation of this technique in which patterned loss masks are machined onto a VECSEL cavity mirror using a Digital Micromirror Device (DMD)-enabled femtosecond-laser ablation system, where the DMD is used as an intensity spatial light mod- ulator. Interaction of the loss mask with the laser mode area results in the VECSEL oscillating preferentially on the spatial modes that observe the least loss within the aperture, and modulation of pump power enables control of the oscillating mode frequency separation. We describe the characteristics of the masks and the properties of the laser operation as progress towards eventual pulsed emission. Our technique has the advan- tages of discrete gain and Semiconductor Saturable Absorber Mirror (SESAM) structures, very fast fabrication times and the ability to fabricate multiple apertures on a single mirror.
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