Development of a Modular, Cost-Optimized Raman Spectrometer for Laboratory and Field Applications

Gabriel White | Argon Aerospace LLC

Date: July 2025

Abstract

This report outlines the design, assembly, and operational objectives of a custom-built Raman spectrometer developed by Argon Aerospace. The system employs modular components, largely sourced from commercial optics suppliers and surplus equipment, to achieve high-resolution Raman spectroscopy suitable for materials characterization and planetary analog studies. The intent of this project is to demonstrate that a functional, research-capable Raman platform can be constructed at a fraction of the cost of commercial systems, enabling broader accessibility to spectroscopic tools in resource-limited academic or field environments.

1. Introduction

Raman spectroscopy is a cornerstone technique in analytical science, valued for its ability to provide rapid, non-destructive insight into molecular structure, chemical bonding, and material composition. When monochromatic light interacts with a sample, a small portion of the photons are inelastically scattered, undergoing energy shifts that correspond to vibrational modes of the molecules present. These shifts form a “fingerprint” spectrum unique to the chemical structure of the material. Raman spectroscopy finds application across materials science, solid-state physics, geology, biology, and planetary science.

However, despite its analytical power, commercial Raman spectrometers are often inaccessible to smaller laboratories and educational institutions due to their high cost, proprietary software, and limited hardware flexibility. Many systems are “black box” instruments that do not allow customization of the optical path or integration with external components, such as automated stages or robotic sample delivery systems.

This project, developed under Argon Aerospace’s Research and Development program, aims to overcome these barriers by building a high-resolution Raman spectrometer using open, modular components. By combining precision optical hardware from vendors such as Thorlabs and Newport with a scientific-grade USB CMOS camera and custom software tools, we demonstrate that a versatile Raman spectrometer can be constructed at a fraction of commercial cost, while preserving functionality suitable for research-grade applications. Special emphasis is placed on expandability: the system can later be adapted for remote sensing, microanalysis, and planetary simulant research—domains critical to Argon Aerospace’s ongoing initiatives in space instrumentation and resource prospecting.

2. System Overview

The Raman spectrometer is designed as a backscattering configuration, optimized for excitation at 532 nm and detection of Raman shifts ranging from ~200 cm⁻¹ to 3000 cm⁻¹. The system is laid out linearly on a 1/4″-20 tapped aluminum optical breadboard, with beam propagation constrained to a planar layout for mechanical stability and ease of alignment.

The architecture is divided into three core subsystems:

2.1 Laser Excitation Pathway

At the front end of the system is a 532 nm diode-pumped solid-state (DPSS) laser module, outputting approximately 100 mW of continuous wave (CW) power. The module is equipped with TTL modulation and active fan cooling for stability and longevity. The beam is directed through a broadband dielectric mirror mounted in a kinematic mount (Thorlabs KM100), which redirects the beam by 90° toward the sample axis. A 50:50 plate beamsplitter (Thorlabs BSW10) mounted in a right-angle bracket (KBT1X1T) splits the excitation beam, transmitting half toward the sample while reflecting the returning Raman-shifted signal toward the spectrometer path.

2.2 Sample Illumination and Signal Collection

The beam is tightly focused onto the sample using a 10x Olympus Plan achromatic microscope objective (NA 0.25, WD 10.6 mm), mounted in an SM1-threaded tube system via an SM1A3 RMS adapter. The sample is mounted on a manually adjustable stage combining a Newport 460A-XY linear platform and a Thorlabs PT1 Z-axis micrometer stage. This provides sub-millimeter positioning control to bring the sample into the laser’s focal plane.

Backscattered light from the sample includes both Rayleigh and Raman components. A long-pass edge filter (Thunder Optics, ~550 nm cut-on) blocks elastically scattered 532 nm light, allowing only Stokes-shifted Raman photons to reach the spectrometer.

2.3 Dispersive Spectrometer and Detection

The filtered Raman signal is passed through a precision variable slit (Thorlabs VA100) to define spectral resolution and limit background noise. It then strikes a ruled reflective diffraction grating (Thorlabs GR25-1800, 1800 lines/mm, blazed at 500 nm), which disperses the light by wavelength. A 50 mm focal length achromatic lens (AC254-050-A) focuses the spectrum onto the sensor of a Thorlabs DCC1545M USB CMOS camera. The camera is operated via Thorlabs’ software or MATLAB interface, capturing high-resolution spectral images for processing.

All optical components are mounted using SM1 lens tube segments, cage plates, posts, and baseplates, ensuring repeatable alignment and mechanical rigidity. The design allows for future modular upgrades including motorized sample stages, alternate excitation sources (e.g., 785 nm diode), and fiber-coupled configurations.

3. Optical and Mechanical Layout

The optical path is organized into three primary subsystems:

3.1. Laser Excitation Train

• Laser Source: 100 mW, 532 nm CW green laser diode with TTL modulation and fan cooling

• Collimation and Steering: A 90° broadband dielectric mirror (Thorlabs BB1-E02) mounted in a KM100 kinematic mount and KBT1X1T base redirects the beam horizontally into a VA5-1064/M 50:50 cube beamsplitter.

3.2. Sample Delivery and Signal Collection

• Objective: Olympus Plan 10x RMS microscope objective, mounted via SM1A3 adapter

• Stage: Newport 460A-XY manual translation stage with PT1 Z-axis focus control

• Filter: Thunder Optics long-pass edge filter (~550 nm) for Rayleigh rejection

  
  

3.3. Spectrometer Module

• Entrance Slit: Thorlabs VA100 precision variable slit

• Dispersive Element: Thorlabs 1800 lines/mm ruled grating (blazed at 500 nm)

• Lens: Thorlabs AC254-050-A achromatic lens (f = 50 mm) to image spectrum onto sensor

• Detector: Thorlabs DCC1545M USB monochrome CMOS camera (1.3 MP)

All components are mounted to a 1/4″-20 optical breadboard using Thorlabs cage systems, post assemblies (TR75, PH2), and appropriate adapters.

4. Software and Data Analysis

Raw spectral data is acquired via Thorlabs’ DCC software or MATLAB Image Acquisition Toolbox. Post-processing scripts convert pixel data to Raman shift (cm⁻¹) using calibration standards such as polystyrene. Final spectra are plotted, filtered, and analyzed using NumPy, SciPy, and Raman-specific libraries.

5. Applications

The instrument is suitable for:

• Materials characterization: Polymers, carbon materials, semiconductors

• Planetary simulant analysis: Martian and lunar regolith analogs

• Organic compound identification: Pharmaceuticals and bioorganics

• Educational demonstration: Undergraduate/graduate optics and spectroscopy labs

6. Conclusion

This project demonstrates that a fully functional Raman spectrometer can be constructed for under $2,000 USD using accessible, modular parts. While this system lacks certain refinements of commercial Raman platforms (e.g., automated mapping stages, cooled detectors), it offers excellent value for academic and field researchers.

Ongoing upgrades include automated Z-focus, fiber-coupled laser injection, and integration of Raman mapping capabilities.

7. Contact & Resources

For more information, schematics, or collaboration inquiries, please contact:

Gabriel White

Principle Engineer and Investigator

📧 gabriel.white@argonaerospace.com