Probing infrared detectors through energy-absorption interferometry

Abstract

We describe an interferometric technique capable of fully characterizing the optical response of few-mode and multi-mode detectors using only power measurements, and its implementation at 1550 nm wavelength. Energy-Absorption Interferometry (EAI) is an experimental procedure where the system under test is excited with two coherent, phase-locked sources. As the relative phase between the sources is varied, a fringe is observed in the detector output. Iterating over source positions, the fringes' complex visibilities allow the two-point detector response function to be retrieved: this correlation function corresponds to the state of coherence to which the detector is maximally sensitive. This detector response function can then be decomposed into a set of natural modes, in which the detector is incoherently sensitive to power. EAI therefore allows the reconstruction of the individual degrees of freedom through which the detector can absorb energy, including their relative sensitivities and full spatial forms. Coupling mechanisms into absorbing structures and their underlying solidstate phenomena can thus be studied, with direct applications in improving current infrared detector technology. EAI has previously been demonstrated for millimeter wavelength. Here, we outline the theoretical basis of EAI, and present a room-temperature 1550 nm wavelength infrared experiment we have constructed. Finally, we discuss how this experimental system will allow us to study optical coupling into fiber-based systems and near-infrared detectors.

Modeling the partially coherent behavior of few-mode far-infrared grating spectrometers

“…From an experimental optics point of view, the HFMF can be used to investigate the few-mode behavior of ultra-sensitive FIR systems, including diffraction and dispersion. Furthermore, because the HFMF relies on the optical modes of the system to propagate correlation matrices, it is well suited for optical experiments related to spatial coherence, such as partially coherent diffractive imaging [34], or probing the few-mode response of optical systems [35]. From a design perspective, there is also a wide range of applications, particularly during the first order design phase of a system.…”

Applying Energy Absorption Interferometry to THz Direct Detectors Using Photomixers

“…We also aim to define the positions of the source probes at the coordinates determined by the desired sampling size and resolution of the detector beam at a focal plane, such that both D(r 1 , r 2 ) and E(r 1 , r 2 ) can be measured in the same basis, and no change of basis operations are required. The definition of D(r 1 , r 2 ) and E(r 1 , r 2 ) in arbitrary locations along the beam propagation axis is possible and is detailed in [12]. This sampling coordinates can be expressed as a set of M x-coordinates x i where i ∈ 1, 2, .…”

“…In this case, there is only a single nonzero a i,m in ( 6) for each source position m. In this way, the source fields e m are linearly independent vectors. For a particular pair of source probe locations m and m , the power measured at the detector can be expressed as [12]…”

“…Further implementations of this technique may use smaller relative aperture sizes and sources with a higher output power to provide a more accurate measurement of the spatial forms of the detector beam modes. If necessary, full characterization and removal of the source beam can be done [12] but is beyond the scope of this work.…”

Characterization of Widefield THz Optics Using Phase Shifting Interferometry

“…To achieve this goal a phase and amplitude measuring system was implemented. Such systems with MKID arrays have been previously demonstrated by [12], [13], and [14], a heterodyne technique, using the interference beat between two frequency offset solid-state multiplier sources with a common phase reference. In this work, we present a novel implementation of a phase and amplitude beam measuring system based in the use of terahertz photonic sources and phase shifting interferometry.…”