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We present a single-mode, low-threshold terahertz quantum cascade laser (QCL) operating on a defect line in a photonic crystal. A 55% reduction in threshold current vs. metal-metal QCLs is due to the slow light effect.
We present two graphene based plasmonic devices for the external optoelectronic amplitude modulation of THz radiation. Modulation depths as high as 8% and up to 50 MHz, for a 10 V potential difference are reported.
We demonstrate a THz optical delivery system capable of supplying a low divergence HE11 Gaussian beam at a distance of >500mm from the facet of a THz quantum cascade laser. This is achieved by optimising the optical coupling to an external hollow flexible polystyrene-lined Ag waveguide, by utilising a monolithically integrated cylindrical metal waveguide in the laser mounting block. This is shown...
We present a quantum cascade laser emitting around 2.9 THz, based on a new hybrid plasmonic waveguide design. The resultant optical mode provides a performance commensurate with a metal-metal waveguide, while improving the far-field pattern.
We have realized a compact beam-shaping and collimating element for a double metal terahertz (THz) quantum cascade laser (QCL) emitting around 2.9 THz using directly integrated hollow metallic waveguides. Our approach allowed us to efficiently improve the beam profile with respect to the standard emission pattern observed out of a double metal QCL. The Gaussian-like mode profile emerging from the...
We report the realization of a confocal THz microscope based on a ∼ 3 THz quantum cascade laser source. A resolution as low as 67 µm is achieved, with a large contrast enhancement allowed by the confocal geometry. The capability of imaging overlayed objects on close-by planes is also demonstrated.
Multi-terahertz transients map out the photonic bandstructure of a plasmonic crystal while ultrastrong coupling with quantized electronic transitions in semiconductor quantum wells is activated within less than a cycle of light.
We present a differential Near-field Scanning Optical Microscope (NSOM) operating with subwavelength resolution in the THz spectral region. The system, which employs a quantum cascade laser emitting at λ =105 μm as source, has been been tested on metal and graphite objects, with a resolution of ~ λ/10.
The work describes a differential near-field scanning optical microscopy (DNSOM) mechanism, which represents a valuable tool for imaging with sub-wavelength resolution. In this approach the acquisition is carried out using squared apertures with dimensions comparable with the wavelength. The aperture, mounted on a xy translational stage driven with piezo-actuators, is scanned in the near field of...
The design of materials to promote the development and/or regeneration of neuronal tissue requires the understanding of the mechanisms by which the underlying substrate topography can modulate neuronal cell differentiation and migration. We recently demonstrated that plastic nanogratings (alternating lines of grooves and ridges of submicrometer size) can effectively change the neuronal polarity state,...
This study demonstrates the first active channel waveguide in Cr:LiSAF6 as a broadband fluorescence source. Planar waveguides are fabricated by He implantation into optically polished 5.5% doped crystals. Channel waveguides with a 5.0 mum ridge height are fabricated out of planar waveguides by photolithographic patterning and subsequent Ar+ sputtering.
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