In the fields of modern scientific research, environmental monitoring, industrial process control, biomedical diagnosis, and national security, there is an increasing demand for rapid, accurate, and non-contact analysis of material composition. Although traditional spectroscopic techniques have been widely used, they face bottlenecks in sensitivity, resolution, and selectivity. Laser Spectrometer, as a revolutionary development in spectral analysis technology, has become a core technology tool in the field of modern precision measurement due to its unique advantages such as high brightness, narrow linewidth, high directionality, and tunability. It has opened a new era of high-sensitivity and high selectivity substance detection.

1、 Basic principles and technical characteristics

A laser spectrometer is an instrument that uses laser as an excitation light source to analyze the energy level structure, molecular vibration, chemical composition, and physical state of a substance by detecting its optical signals such as absorption, emission, scattering, or fluorescence after interacting with the substance. Its core lies in "laser+spectroscopy", which deeply integrates the excellent characteristics of laser with the analytical ability of spectroscopy.

Compared with traditional broadband light sources such as tungsten lamps and deuterium lamps, lasers have the following significant advantages:

-High monochromaticity: The spectral line width is extremely narrow (up to the MHz or even kHz level), which can accurately match the transition energy levels of specific atoms or molecules, greatly improving selectivity.

-High brightness and directionality: Energy concentration enables detection of samples at long distances, micro areas, or low concentrations.

-Tunability: By adjusting temperature, current, or external cavity, the wavelength can be continuously adjusted to cover specific absorption spectral lines, making it suitable for trace gas detection.

-Coherence and Ultra Short Pulses: Supports nonlinear spectroscopy, time-resolved measurements, and ultrafast dynamics research.

2、 Main types and working methods

According to the mechanism of interaction between laser and matter, laser spectrometers can be divided into various types, each with its own characteristics:

1. Laser absorption spectroscopy (LAS) and tunable diode laser absorption spectroscopy (TDLAS)

Scan the characteristic absorption lines of target molecules using laser wavelength and calculate the concentration using the Beer Lambert law. TDLAS technology is widely used in flue gas emissions such as CO, CO ₂ NOx）、 The detection limit for industrial process gases (O ₂, CH ₄) and atmospheric environment monitoring can reach ppb (parts per billion) level.

2. Laser induced fluorescence spectroscopy (LIF)

Laser excites atoms or molecules to a high-energy state and emits fluorescence when they return to the ground state. Qualitative and quantitative analysis is performed by detecting the fluorescence intensity and wavelength. LIF sensitivity is commonly used for combustion diagnosis, free radical detection, biomarker analysis, and single-cell imaging.

3. Laser Raman Spectroscopy

Obtain molecular "fingerprint" spectra based on the inelastic scattering effect of laser and molecular vibration/rotation energy levels. Confocal laser Raman microscopy can achieve microscale spatial resolution in chemical imaging, and is widely used in materials science, drug analysis, cultural relic identification, and forensic science.

4. Laser induced breakdown spectroscopy (LIBS)

High power pulsed laser focuses on the surface of the sample, generating high-temperature plasma. By analyzing the atomic/ion spectral lines emitted by the plasma, rapid detection of elemental composition is achieved. LIBS does not require sample pretreatment and can perform in-situ and online analysis of solids, liquids, and gases. It is applied in metallurgy, geology, nuclear industry, and space exploration (such as the Mars rover ChemCam).

5. cavity enhanced spectroscopy (such as CEAS, OF-CEAS) and cavity ring down spectroscopy (CRDS)

Injecting laser into a high reflectivity optical cavity results in a path length of several kilometers, greatly enhancing the absorption signal. CRDS calculates the absorption coefficient by measuring the time of laser attenuation inside the cavity, with a sensitivity of up to ppt (parts per trillion), and is currently one of the absorption spectroscopy technologies.

3、 Technical advantages and application areas

1. Ultra high sensitivity and detection limit

It can detect trace pollutants, rare isotopes, or low concentration biomolecules, meeting strict requirements in the fields of environment and health.

2. High selectivity and strong anti-interference ability

The laser wavelength can accurately match the characteristic spectral lines of the target object, effectively avoiding background interference.

3. Non contact and non-destructive testing

Suitable for remote measurement of precious cultural relics, living tissues, high temperatures, or hazardous environments.

4. Real time online monitoring

Can be integrated into industrial pipelines or environmental monitoring stations to achieve continuous and automated analysis.

5. Multi functionality and miniaturization trend

The development from large-scale laboratory equipment to portable, handheld, and even chip level spectrometers has expanded the application boundaries.

Typical applications include:

-Environmental monitoring: detection of atmospheric pollutants, greenhouse gases, and heavy metals in water quality.

-Industrial process control: gas composition monitoring in petrochemical, steel, and semiconductor manufacturing.

-Biomedical: Breath analysis (such as acetone, NO), blood testing, early cancer screening.

-Public safety: rapid identification of explosives and chemical warfare agents.

-Frontiers of scientific research: cold atom physics, quantum sensing, and astrochemical analysis.

Laser spectrometer is not only the "eye" of scientific exploration, but also the "sentinel" of protecting the environment, safeguarding health, and promoting industrial upgrading. With the continuous breakthroughs in laser technology and photon integration, laser spectrometers will play an increasingly important role in national strategic needs such as precision medicine, smart cities, and carbon neutrality monitoring, illuminating the microscopic mysteries of the material world.