The Detect Theme is dedicated to the integration of metasurfaces into photodetectors to expand their functionality and develop the next generation of imaging systems from the visible to the LWIR regions. Electromagnetic waves carry a wealth of information in the form of spectral content, polarisation and phase that cannot be directly accessed with current detection technologies that sense only intensity. This ‘hidden’ knowledge is central to applications in areas as diverse as LIDAR, remote sensing, in-vivo imaging of biological tissue, optical communications, microscopy of living cells and the identification of objects for machine vision. The filters and other optical components required to tap this extensive information add to the size, complexity and cost of optical systems and increasing attractive computational methods also require energy and compromise speed.
Furthermore, although silicon-based photosensors are inexpensive and widely available, these sense only short-wavelength visible light and access to longer wavelengths in the near, short-wave, mid-wave and longwave infrared regions of the spectrum requires expensive, bulky and noisy detectors. Yet this region of the spectrum is an enabler for major applications in Industry 4.0 such as night vision, passive thermal imaging, and imaging through objects opaque to visible light.
Detect comprises sub-programs of work that will develop meta-optical devices for advanced multi-modal detection and their integration into non-imaging detectors and meta-optical enhanced imaging harnessing the visible and infrared spectral radiation bands. Metasurfaces will revolutionise access to hitherto unavailable optical information and deliver ultra-compact optical components. This will result in savings in cost, materials and energy in manufacturing and expand access to state-of-the-art devices.
Recent achievements
- Demonstration of dual (visible and NIR) GaAsSb Nanowire Array multiwavelength photodetectors along with their application to RGB colour imaging.
- Demonstration of a InGaAs/InP multi-QW photoconductive photodetector with high room temperature responsivity (14.5 A/W @1550 nm).
- Demonstration of highly uniform multiple QW nanowire growth which is critical for NW-QWIP fabrication.
- Demonstration of a device that can discriminate between different angles of incidence on a metasurface and its application to phase contrast imaging of optical wavefields and microscopy of biological cells.
Subprogram 3A – Advanced Infrared Imaging
This research endeavours to poineer the development of next-generation infrared detectors by leveraging novel semiconductor materials pecifically employing III-V compounds like InAs, InGaAs and InP grown by MOCVD and MBE machine into nanowires and quantum wells, operating within shortwave (SW) and midwave (MW) spectral bands.
We have achieved a breakthrough in the fabrication of III-V based nanowire infrared detectors. By refining fabrication techniques, we have successfully produced a small dimension InGaAs nanowire array photodetector measuring 50×50 um, aimed at enhancing the performance of shortwave infrared (SWIR) photodetection. This innovative detector exhibits reduced dark current, enabling the detection of signals at lower power levels and higher temperatures compared to previous iterations.
Researchers have also achieved a significant milestone by successfully fabricating a high-performance shortwave infrared (SWIR) detector utilizing InGaAs/InP core-shell nanowire technology. This breakthrough entails the fabrication of a 4×4 array of InGaAs/InP nanowire photodetectors, demonstrating exceptional responsivity exceeding 1A/W within the SWIR spectral band spanning from 1000nm to 1600nm.
Our team have also successfully developed a new type of infrared photodetector—called the nanowire QWIP—that operates in the midwave infrared range (3–5 μm). Thanks to its unique nanowire design, it can detect light from straight on (normal incidence), which is a major advancement. After careful testing at our UWA node, the device showed strong performance at 4.2 μm, with high sensitivity and low noise—paving the way for future applications in areas like thermal imaging and remote sensing.
Action Items for 2024:
- Experimental demonstration of short infrared (SWIR) single-pixel imaging using nanomaterial-based photodetector
- Demonstrate metasurface/ GaAsSb nanowire array single pixel polarisation imaging
- Fabrication of a hybridised 2×2- superpixel metalens array with an MCT imaging array
Subprogram 3B – Seeing the Invisible with Nanotechnology
The second Detect subtheme focuses on research that uses nanotechnology to extract information from light. Light carries a vast amount of ‘hidden’ information that is crucial for applications such as agriculture, pharmaceutical production, medical diagnostics, environmental monitoring and machine vision. We create meta-optical systems that permit accessing and measuring these properties of light.
Our work towards nanotechnology-enabled light detection application includes identifying chemicals based on the way they interact with light by engineering a micrometer-sized device able to perform this analysis by leveraging nanotechnology and artificial intelligence algorithms. These ‘micro spectrometers’ could enable low-cost and mobile chemical detection in future handheld devices.
We are also developing highly compact photodetectors that can efficiently determine the polarisation of light in an image in the infrared spectral region are challenging to create. We have numerically demonstrated that nanometer sized sheets of InAs semiconductor can successfully achieve this task. We are currently working on the experimental implementation of these structures.
Action Items for 2024:
- Experimental demonstration of gas sensing using quasi bound mode in the continuum filters integrated with a detector array
- Demonstrate tunability of graphene in a gated structure
- Progress experimental demonstration of ghost imaging of transparent objects