Let’s build a STAMP system!

First, build a pump–probe imaging setup as shown in Fig. 1. Split the 1030-nm ultrashort pulse, using one for the excitation of phenomena (pump) and the other for observation (probe). By converting the probe pulse into a 515-nm second-harmonic pulse with a nonlinear crystal, you can use a general camera instead of an infrared camera (with improved spatial resolution). You can add a bandpass filter centered at 515 nm to prevent scattered light at 1030 nm, if necessary.

Once you include a delay line to adjust the arrival time between the pump and probe pulses, the pump–probe imaging system is complete.

--Did you get an image?

Now, let's extend the pump–probe method, which acquires a single image, into STAMP, which enables the acquisition of a motion image. First, we introduce the temporal mapping device (TMD), a key component of STAMP. Since we aim to observe phenomena in the picosecond time regime, we add a grating pair as the TMD.

Grating pairs can be used either as a stretcher, which temporally stretches an ultrashort pulse, or as a compressor, which compresses a stretched pulse. The compressor configuration is simpler, so let's use it here. By adjusting the grating separation, you can tune a temporal delay of several hundred picoseconds. It is a common optical setup, so you can find plenty of information by searching the web. 

Examples of products (optics) of the configuration are listed below.

• Diffraction grating 1: GH25-24 V (Thorlabs)

• Diffraction grating 2: GH50-24 V (Thorlabs)

If inserting the grating pair causes the probe pulse to arrive with a significant delay, extend the optical path on the pump side accordingly. At this point, it is fine if you acquire a motion-blurred image.

Then, we introduce a spatial mapping device (SMD). As the SMD, you can use a spectral imaging system with high wavelength resolution. 

Here, we use a spectral filtering system with a simple, compact configuration. As shown in Fig. 3, it consists of a diffractive optical element (DOE) that splits the beam in two dimensions, a narrowband bandpass filter that is placed at a tilted angle, and a lens. By placing the DOE at the focal distance f of the lens, the optical axes of the beams split by the DOE are made parallel.

In addition, an iris is placed at a conjugate plane of the original imaging system to limit the field of view of each frame projected onto the image sensor. This conjugate plane is then imaged onto the image sensor using the newly introduced lens.

Examples of products (optics) of the configuration are listed below.

• DOE: DE-R 352 (HOLOEYE)

• Bandpass filter: 532.0–1 OD6 Ultra Narrow Bandpass Filter (Alluxa)

• Lens: AC254-045-A (Thorlabs)

That’s it! --Were you able to capture the ultrafast motion pictures?

You can change the recording time window by selecting a TMD from the options listed below, but not limited to. The timescales are approximate.

• fs timescales: glass plate, prism pair, chirp mirror

• ps timescales: glass rod, fiber bragg grating, grating pair

• ns timescales:  FACED, Spectrum circuit, Spectrum shuttle

To acquire a larger number of frames, a broader spectral bandwidth is preferable. Several spectral broadening techniques based on nonlinear effects are available; please apply them as needed.