Two Spectrometers on a Chip

The promise of miniaturized millimeter-wave (mmw) spectrometers to provide sensitive and highly specific detections of volatile materials in normal and extreme environments has recently been demonstrated in the Spectrometer-on-a-Chip (SpecChip) project. These efforts show that specific organic and inorganic species are readily identified and quantified utilizing a miniaturized Fabry-Perot cavity coupled to a single circuit board containing the mmw production and detection circuitry. These efforts also quantified the sensitivity of the system, the bandwidth, and identified the limiting technologies. Building upon this success, we propose here to improve the extend the bandwidth and range of the supporting CMOS technology to support science goals. We push the boundary of two technological limiting factors for mini-mmw spectrometers (1) to extend the coverage in W-band (covering HDO at 80.6 GHz) and (2) to provide frequency coverage up to G-band (for H2O at 183 GHz). The two chipsets will be shown to operate in a single system, the SpecChip^2. These developments enable the highly desirable science targets of quantifying both water (H2O) and deuterated water (HDO). These measurements in tandem enable H/D ratio measurements in water/ice samples and expand the existing ability to detect and quantify organic and inorganic volatiles. The improvement in frequency range and bandwidth also expands the applicability of CMOS spectrometers to enantiomeric specific measurements. The demonstrated low-mass, low power millimeter wave system with CMOS components covers 89-104 GHz and gas detections of CH3OH, CH3CHO, N2O, OCS, CH3CH2OH, CH3CN, CH3CH2CN, (CH3)2CO, NaCl and KCl have been made. The demonstrations are limited by sample availability and are only a fraction of the gases detectable with such a system. However, there are key species of scientific interest whose target transitions are at higher frequencies, particularly H2O at 183 GHz (in G-band 140-220 GHz) and HDO at 80.6 GHz (in W-band 75-110 GHz). Thus far, 65 nm CMOS tunable devices with sufficient ( > 1 mW) power to pump a mixer or a molecular transition, have not been demonstrated above 140 GHz. For infusion of this technique into space missions, we must be able to achieve detections for the highest-value science targets, therefore we propose to develop, fabricate and test the necessary circuitry in 28 nm CMOS, an architecture that is showing improvements for upper frequency limits. Through creation of the specific W-band and G-band circuitry necessary for planetary science instrumentation, we provide a broadly useful new instrument with a premier science capability for water H/D ratio measurement. More »