Raman spectroscopy is one of the most versatile tools for fast, non-destructive chemical analysis.
By illuminating a sample with a single-frequency laser and analyzing the scattered light, it's possible to identify molecular structures and distinguish materials from their unique spectral fingerprint — without touching or damaging the sample.
The quality of that fingerprint, however, depends heavily on the excitation laser itself. Wavelength, spectral linewidth, and power stability all shape how clean — and how usable — the resulting spectrum is.
Time-resolved Raman spectroscopy (TRRS) uses the timing of scattered photons — not just their wavelength — to get a cleaner measurement.
The best-established and most practical version of this is time-gated Raman spectroscopy, which uses pulsed excitation to reject fluorescence background.
The biggest obstacle in real-world Raman measurements isn't the Raman signal itself — it's fluorescence.
Many samples emit fluoresce light under laser excitation, producing a broad background that can be orders of magnitude stronger than the Raman signal hiding underneath it.
In organic materials, polymers, and biological samples — some of the most valuable application areas for Raman — this fluorescence background can bury the spectrum entirely.
There are a few pragmatic ways to overcome the fluorescence problem:
Shift to near-infrared excitation (785 nm, 1064 nm), where fluorescence is weaker — but Raman scattering efficiency falls off sharply with wavelength (roughly λ⁻⁴), so signals get weaker and measurements slower.
Shift to UV excitation (below ~250 nm), which suppresses fluorescence and boosts Raman efficiency — at the cost of higher system complexity, added optical losses, and a real risk of photochemical sample damage.
Separate the signals in time — time-gated Raman spectroscopy.
Raman scattering happens essentially instantaneously with the excitation pulse. Fluorescence doesn't — it builds up and decays over hundreds of picoseconds to several nanoseconds, depending on the material. A short excitation pulse and a fast detection gate capture the Raman signal at the leading edge, before the fluorescence background has had time to accumulate.
Time-gated Raman spectroscopy exploits that timing gap: illuminate the sample with a short laser pulse, then collect scattered light only in the narrow time window immediately after excitation. The Raman signal comes through; most of the fluorescence is gated out before it arrives.
This lets you keep the strong Raman efficiency of visible-wavelength excitation while sidestepping the fluorescence that normally rules it out — a combination that's particularly valuable for biological samples, pharmaceutical analysis, and other fluorescence-heavy materials where conventional Raman falls short.
A note on scope: "time-resolved Raman" is sometimes also used for pump-probe techniques that track excited-state or reaction dynamics on ultrafast timescales — a different application from fluorescence rejection.
This page, and related laser platform, is focused specifically on time-gated fluorescence suppression; talk to us if your application needs synchronized pump-probe excitation and we can discuss what's possible.
Time-gating shifts a lot of the engineering requirements onto the excitation source.
To make it work, the laser needs to deliver on several fronts at once:
Short pulse duration
Pulses in the 50–100 ps range let the detection window close before the fluorescence background has meaningfully developed — this is what makes the technique effective in the first place. Where a sample needs an even tighter gate, pulse duration can be shortened to 50 ps.
Spectral purity
Raman spectroscopy measures tiny wavelength shifts relative to the excitation line, so a narrow, stable, single-frequency spectrum is essential for resolution and repeatable measurements from run to run.
Pulse-to-pulse stability and beam quality
Time-gated detection only captures a narrow slice of each pulse, so shot-to-shot energy fluctuations show up directly as spectral noise and baseline drift.
Tight power stability (< 2% standard deviation) and diffraction-limited beam quality (M² < 1.3) keep spectra reproducible and coupling efficient.
Compact size, low maintenance, and long-term stability
A small footprint and minimal upkeep benefit lab and OEM users alike — keeping benchtop research instruments simple to operate, and integrated OEM systems reliable over continuous use.
Meeting all of these simultaneously — short pulses, spectral purity, stability, and a small footprint — is a genuinely hard engineering problem, which is exactly why it's the problem we built our laser platform to solve.
Picophotonics' picosecond microchip lasers are built around proprietary SESAM-based passive Q-switching — a technology that generates highly stable, single-frequency picosecond pulses from a compact, monolithic microchip architecture, without the cost or complexity of a mode-locked laser system.
For time-gated Raman specifically, two platforms cover the range most instrument builders need:
CP32 - 532 nm high energy picosecond laser
Single-frequency operation with short pulse durations (down to 50 ps) and adjustable pulse energy up to several µJ, giving you room to tune excitation conditions to the sample without sacrificing pulse duration or spectral purity.
This is our recommended platform where higher signal levels, longer working distances or additional flexibility are needed.
CP32 Product Page
SP05 — 532 nm OEM green laser.
A lower-energy, application-ready platform for instrument builders who need the same 532 nm, short-pulse performance in a cost-optimized, evaluation-friendly package — a practical starting point for prototyping a time-gated Raman instrument before scaling up.
SP05 Product Page
1064 nm and dual-wavelength options
For samples where residual fluorescence remains an issue even with time-gating, the same platform is available at 1064 nm, where fluorescence excitation is intrinsically weaker. Pulse energy is configurable to several µJ on either wavelength, and dual-wavelength 532/1064 nm output is available where an experiment benefits from two excitation bands from a single, timing-matched source.
Proven technology
Our picosecond laser technology have already been used to build time-gated, fluorescence-rejecting Raman instrumentation in published research — including a time-resolved Raman spectrometer developed at the University of Oulu, which combined a SESAM Q-switched microchip laser with a CMOS SPAD line sensor to achieve high fluorescence rejection.
Time-Resolved Raman Spectrometer With High Fluorescence Rejection Based on a CMOS SPAD Line Sensor and a 573-nm Pulsed Laser
2021, T. Talala et al., University of Oulu
https://ieeexplore.ieee.org/abstract/document/9335980
Talk to us about your Raman application
Every Raman instrument has its own constraints — sample type, required acquisition speed, integration footprint, and budget all shape which laser platform fits best.
If you're developing a time-resolved or time-gated Raman system, our team can help you match pulse duration, energy, and form factor to your application, or scope a custom configuration if the standard platforms don't quite fit.
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