* Probing around the fundamental wavelength (~800 nm for Ti:Sapphire and ~1030 nm for Yb) requires manual filter adjustments.

The nanosecond window is achieved by using a direct-drive high-speed optical delay line. Custom-designed mounts are employed for the delay line optics to increase the beam alignment reproducibility and overall reliability. This delay line features high resolution as well as high speed. Scanning at high speeds is very important because it allows for pseudo-random stepping without a significant increase in the experiment time. This type of stepping is very useful for minimizing the effects of laser instability and sample degradation.

The standard 8 ns time window is extendable to milliseconds with the EOS add-on.

FastScan is a cutting-edge technique that greatly improves the data collection efficiency in transient absorption.

With FastScan, transient spectra are collected continuously as the delay line moves down the track. This means every laser pulse is registered as the data collection does not pause for the delay stage to move from one-time point to another.

This technique offers several major advantages:

• The data acquisition time is shortened significantly, especially at the higher laser rep rates. Even at 1 kHz, the data collection is ~3 times faster with FastScan.
• With easily photodegradable samples, you can get a quick preview of the full dynamic surface in just seconds before committing to running a full experiment.
• Since each delay scan only takes seconds, it is much easier to catch the moment when something goes wrong and still save the good data. For example, if your sample starts to degrade, etc.
• Since many more time scans are averaged to get the final dynamic surface, things like pump noise get averaged out much better so your resulting kinetic traces are cleaner and more reliable.

This short video illustrates how FastScan works.

We use off-axis parabolic reflectors to collimate and focus the probe light in Helios. This results in a ~50 µm probe beam waist at the sample. Focusing the probe beam tightly allows to use low energy excitation, down to tens of nJ/pulse, without sacrificing signal amplitudes.

Also, using reflective optics in the probe path improves the time resolution of the setup.

• Automated optical delay line alignment (Smart Delay LineTM).

• Automated switching between UV, VIS, NIR, and SWIR spectral ranges.

• Automated Pump Beam Alignment.

All Helios detectors are fiber-coupled spectrographs with linear array detectors. Each spectrograph has an aberration-corrected concave grating for maximum light throughput (essential for high quality data). The ADC resolution is up to 16 bit. All detectors are mounted in a 19” electronics rack outside the optical bench.

UV-VIS. We have two detector options for this spectral range:

• CMOS. This 1024 pixel CMOS sensor is ideal for higher speed data acquisition. Allows for individual laser pulse detection for up to 5 kHz. Spectral response: 200 – 1000 nm. Typical spectral range spans 600 nm (ie. 350 – 950 nm).

• CCD. This 2048 pixel back-thinned CCD sensor is ideal for 1 – 2 kHz lasers and features very high sensitivity as well as the dynamic range. Spectral response: 200 – 1000 nm. Typical spectral range spans 600 nm (ie. 350 – 950 nm). Spectral acquisition rate – up to 2000 spectra/s.

NIR spectral range. This 256 pixel InGaAs sensor presents a great balance between spectral resolution and sensitivity. Spectral response: 800 – 1600 nm. Typical spectral range spans 800 nm (ie. 800 – 1600 nm). Spectral acquisition rate – up to 5000 spectra/s.

SWIR spectral range. 256 pixel InGaAs sensor (spectral response: 1000 – 2600 nm). Typical spectral range spans 800 nm (ie. 1600 – 2400 nm). Spectral acquisition rate – up to 5000 spectra/s.

The spacious (350 mm x 250 mm) sample compartment and the removable side panels allow for easy mounting of cryostats, translating sample holders and even coupling to external magnets. Also, simply having more space around the sample makes working with your samples easier.

The magnetic stirrer allows for working with closed cuvettes (≥2 mm long) and can work with a simple cuvette holder. The translating sample holder can raster thinner cuvettes (which cannot be stirred easily), films, wafers, etc. The translating sample holder can work with transmissive as well as reflective samples.

HELIOS has an option for second probe (reference) channel. In this case, the probe beam is split into two before passing through the sample. While one arm travels through the sample, the other is sent directly to the reference spectrometer that monitors the fluctuations in the probe beam intensity. The main advantage of this approach is that it allows the user to achieve the specified signal-to-noise ratio with a lower number of averaged laser pulses. This method is recommended for experiments with low repetition rate and/or easily photodegradable samples where the number of laser shots is strongly limited.

for varying pump energy, etc.

for varying pump energy, etc.

for varying pump energy, etc.

We offer two options for performing spatially resolved transient absorption measurements.

The HELIOS data acquisition software has built-in support for the automated alignment of all critical optical elements for largely hands-off operation.

Helios IR can be used to monitor photoinduced species absorbing in the mid-infrared spectral region. For example, vibrationally excited states, charge carriers and electronically excited states in low band gap nanomaterials, etc.