In this Q&A, we explore some of the breakthroughs that have allowed spectrometers to be reduced in size while maintaining their effectiveness out in the field.
Although spectroscopy has historically involved bringing samples to the instruments,
However, miniaturization still has limits, and designers have to balance the reduction in size against optical performance, so that instruments stay reliable out in the field. As spectrometers move into everyday objects and wearable technology, a growing number of measurements may no longer need a traditional laboratory at all.
In this Q&A, we explore some of the breakthroughs that have allowed spectrometers to be reduced in size while maintaining their effectiveness out in the field.
For most of the 20th century, spectroscopy required bench-mounted instruments weighing as much as a small refrigerator.1 The shift to field-portable devices has occurred in three main generations.2
The first generation included briefcase-sized units that relied on reflective Czerny-Turner spectrographs and fiber-optic coupling.1,2 In the second generation, designers eliminated fiber optics in favor of free-space optical coupling, reducing instrument volume while improving signal-to-noise ratios (S/N) by roughly five times.1,2 The third generation introduced transmission gratings that improved S/N by as much as ten times over earlier reflection designs.1,2 By offloading internal displays and computing systems to paired smartphones, manufacturers reduced Raman units to ~6 cm in length and 63 grams in weight, which is a size reduction of more than 1,000 times compared to early portable systems.1,2
Parallel fabrication advances in microelectromechanical systems (MEMS), resonant-cavity detector arrays, and silicon-nitride photonic integrated circuits (PICs) have similarly allowed
Each technique addresses distinct analytical needs based on its underlying physics. Handheld FT-IR focuses on surface and coating chemistry.1 It is widely used in aerospace manufacturing to verify anodized aluminum layers or confirm primer formulations on composite aircraft panels without destroying components.1
Handheld Raman excels at contact-free molecular identification through transparent containers, making it dominant in pharmaceutical raw-material verification and narcotics screening.1 When paired with surface-enhanced Raman spectroscopy (SERS), which uses silver or gold nanostructures to amplify weak signals, it can detect trace levels of lethal substances such as fentanyl.1,2
Miniaturized NIR spectroscopy serves as a low-cost, high-volume screening tool.1 It is often used to verify food authenticity and screen agricultural products.1
Meanwhile, handheld XRF spectroscopy is often used for elemental analysis. Routine applications include rapid scrap metal sorting and nondestructive analysis in art conservation.1 Advanced benchtop XRF units equipped with doubly curved crystal (DCC) optics now deliver regulatory-grade heavy-metal screening (Pb, Cd, As, Hg) in food matrices.5
Instrument miniaturization faces hard limits imposed by photon physics and ergonomics. For example, a spectrometer must collect sufficient scattered or transmitted photons to produce an acceptable S/N within a reasonable exposure time.1,2 When a spectrometer’s optics are shrunk too far, manufacturers must contend with trade-offs among spectral resolution, coverage range, and measurement speed.1,2 Long-wavelength 1064-nm Raman systems require indium gallium arsenide (InGaAs) array detectors, which are physically larger and heavier than the silicon charge-coupled device (CCD) arrays used in 785-nm instruments.2 Standalone field devices operated by workers wearing protective gloves require readable screens and raised molded buttons, establishing a practical minimum size (~20 × 15 × 10 cm) unless display and control functions are offloaded to an external mobile device.1,2
Recent optical architectures bypass traditional slit-and-grating designs entirely, starting with silicon-nitride PICs. On-chip Fourier transform Raman spectrometers fold the entire optical path onto a fingernail-sized silicon chip using arrays of waveguide interferometers or micro-ring resonators, enabling deployment in wearables, drones, and spacecraft.2–4 Meanwhile, spatial heterodyne spectroscopy (SHS) replaces the narrow entrance slit of a dispersive spectrograph with a pair of diffraction gratings that form an interference pattern.3 This dramatically increases light-gathering capacity (étendue), yielding ~10× sensitivity gains without moving parts.3
Finally, single-photon avalanche diode (SPAD) arrays synchronize detector gating with laser pulses.2 Because Raman scattering is instantaneous while fluorescence is slightly delayed, SPADs suppress background fluorescence in hardware without relying on mathematical baseline algorithms.2
Artificial intelligence (AI) is no longer merely a post-processing tool. It is now designed alongside the optics as a functional part of the measurement chain.3 Techniques like External Variable Augmented Iterative Optimization Technology (EVA-IOT) reduce the reference sample data needed to build a robust pharmaceutical powder-stream model by up to 97%.4 Convolutional neural networks (CNNs) identify chemical warfare agent simulants and differentiate structurally similar synthetic cannabinoids directly from raw spectra without requiring manual baseline subtraction or peak picking.3 Fusing NIR and Raman spectral channels through machine-learning (ML) models enables real-time, automated feed adjustments in bioreactor fermentations, while model-maintenance frameworks automatically correct for calibration drift over weeks of continuous operation.4
