Short‐Wave Infrared Chip‐Spectrometer by Using Laser Direct‐Writing Grayscale Lithography

Abstract

Short-wave infrared (SWIR) spectrometer has been a critical device in spectral analysis fields like agriculture, [1,2] environmental monitoring, [3] astronomy, [4,5] etc. Conventionally, the infrared spectrometer is bulky and delicate due to the spectral division device, such as grating and prism, which limited its applications. The demand and potential for compact spectrometers are enormous for portable and on-chip applications like smartphone spectrometer, [6,7] hyperspectral imaging, [8][9][10] etc. The key to miniaturizing spectrometers is replacing the bulky spectral split devices with miniature photonic devices. [11] Besides, combing with reconstruction algorithms such as compressed sensing and machine learning, the incident light spectrum can be reconstructed with a few numbers of filters. [8,[12][13][14] In recent years, such reconstructive micospectrometer based on Si-based complementary metal-oxide-semiconductor (CMOS) sensors in visible range are primarily investigated. In comparison, the microspectrometer in SWIR range is much more useful to acquire object information in practical applications. Strategies based on photonic devices slab, [9,10,[15][16][17][18][19] quantum dot (QD) slab, [20][21][22] nanowire, [23,24] have been proposed for portable and on-chip microspectrometer. The number and variety of filter spectra determined the resolution of reconstructive microspectrometer. Micro-nano photonic device filters like photonic crystal (PC), metamaterial, Fabry-Perot (FP) cavities can acquire distinctive spectra by varying structure morphology parameters. Material-based filters like QD slab can acquire different spectra by adjusting their size, composition, or bias. Those filters mentioned above are usually fabricated onto a separated slab and then pasted or bonded with a detector chip. In practical applications, the separated slab is fragile and difficult to well-matching with detector pixels, leading to spectral crosstalk and other problems. Recently proposed detector-only reconstructive microspectrometer based on nanowires, [23,24] black phosphorus [25] is ultra-compact without external filters. It has a stable structure with wavelength scale size, but the number of response spectra is hard to increase significantly and limits its resolution.Among these micro-nano filters, FP microcavities array has low spectral correlation coefficient by varying its cavity length, Short-wave infrared (SWIR) information is critical for material analysis, imaging sensing, and other fields. To acquire SWIR spectrum with compact devices, strategies for reconstructive microspectrometer have emerged, such as photonic crystal and quantum dot filter. However, the current SWIR microspectrometer needs many filters with insufficient resolution. In this work, the authors develop a SWIR chip-spectrometer based on Fabry-Perot microcavities array which can be fabricated by using fast and low-cost UV laser directwriting grayscale lithography. The ultra-compact chip-spectrometer can work in a very wide range from 900 to 1700 nm wi...

A mid-infrared high-performance spectropolarimetry filter based on dual-mode independent modulation

“…Full-dielectric FP cavities are currently a standard method for obtaining high-resolution spectra, which have the advantages of freely modifiable wavelengths and easy integration. [27][28][29] A FP structure (top in Fig. 1a) can typically be expressed as Sub|(LH) m 2L(HL) m , where Sub is the Si substrate, L is 482 nm SiO with n SiO = 1.92, H is 270 nm Si with n Si = 3.43, and the (HL) pair number m is set as 5.…”

Emerging Computational Micro‐Spectrometers — From Complex System Integration to Simple In Situ Modulation

“…The strong data processing software capabilities compensate for potential compromises in device performance arising from reduced hardware sizes. Table 1 , [ 16,19,24–26 ] Table 2 , [ 27–33 ] Table 3 , [ 15,34–66 ] and Table 4 [ 67–71 ] compare the performance indicators such as footprint, spectrum range and resolution of spectrometers based on conventional, mapping of spectrum to space, spectrum response modulation, and single detector strategies, respectively. Although miniaturized spectrometers based on spectrum‐to‐space mapping strategy generally achieve spectrum resolution comparable to conventional spectrometers, their footprints still cannot meet the miniaturization requirements.…”

Near‐Infrared InGaAs Intelligent Spectral Sensor by 3D Heterogeneous Hybrid Integration

“…Various filter schemes based on thin-film FP cavity, photonic crystals, and metasurfaces have been demonstrated. [11][12][13][14][15][16][17][18] Linear variable filter (LVF) is a notable example, which has extremely compact and rugged structure with no moving parts. Integrated with array detector, LVF-based spectral sensor can provide a good optical throughput and the capacity to achieve a very short time of spectra acquisition.…”

“…[1] In addition, the reconstruction algorithms such as compressed sensing and machine learning have also been introduced in the computational spectral sensors to achieve the spectral super-resolution. [16,18] Unfortunately, such spectral sensors are primarily investigated based on the CMOS in the visible region, and they are also non-intelligent without integration of data analysis.…”