- Customer Interview: Claudius Riek
- New Video: Introduction to LabOne
- Software Trigger as a multichannel imaging tool
- Squelch for phase measurements
Welcome to the final Zurich Instruments newsletter for 2015.
In October we reached a major milestone, with the shipment of the 1000th HF2LI - some of you may have seen the snapshot of our small celebration on our Facebook page. CTO Flavio Heer said it had been a remarkable journey since the three founders launched the product from a small office here in Zurich’s Technopark, and looked forward to shipment of the 1000th UHFLI and MFLI coming much sooner than it had taken to get to HF2LI #1000!
As a sign of our ongoing development and refinement of our instruments, we recently made the LabOne user interface available for the HF2LI. All new instruments are shipped with this capability and existing users can take advantage of a variety of upgrade paths. With this development the user interface for all of our instruments will have the same look and feel, meaning that customers will be easily able to switch between using devices and even run the same programs.
Looking ahead to 2016, the next major step for Zurich Instruments will be the opening of a new office in Shanghai, PRC. From here we will be able to offer even better support to our customers and sales partners. Look out for a formal announcement in the first half of 2016.
We are also going to be launching some great new products to complement our existing instruments and options. These will include the UHF-AWG, an arbitrary waveform generator option for the Zurich Instruments UHFLI, a 600 MHz lock-in amplifier. Enabling advanced signal and sequence generation, combined with signal analysis, in one instrument, this will be of particular interest to the quantum science community and NMR researchers.
To all of our customers, friends and associates, the whole Zurich Instruments team offers our best wishes for a peaceful, successful and happy 2016.
Customer Interview: Claudius Riek
Hi Claudius, congratulations on your exciting recent results. Before we delve into that, what was your main motivation to choose THz spectroscopy as a field of research? Would you do it again?
Hi Jan, thank you. I got really excited about time-domain multi-THz spectroscopy during my master thesis. At that time I learned that by using the technique of electro-optic sampling you can observe the oscillation of electromagnetic field in amplitude and phase and not only in the intensity. Speaking in terms of measurement equipment you have an oscilloscope for light pulses. For me it is amazing to investigate ultrafast phenomenons on a sub-cycle timescale.
So, at least for a physicist, THz spectroscopy sounds like something with real-world applications. Can you describe that moment when you realized that you were after something rather fundamental the measurement of vacuum field fluctuations?
From the beginning of my Phd thesis at the Chair of Prof. Leitenstorfer at the University of Konstanz the goal was to improve the sensitivity of electro-optic sampling into a regime where we can measure electric fields of only a few V/cm at central frequencies of up to 100 THz - which is very high for that technique. After we realized that we measure electric fields which correspond to less than 1/1000 photons per pulse we switched off our multi-THz field. Now we were only looking for signals from empty space - and saw vacuum fluctuations!
What is the key conclusion from your measurement described in the Science paper? What came as a surprise to you?
The main insight of our Science paper is that electric-field vacuum fluctuations can be measured directly. But only if you look on an averaging volume which is smaller than half the oscillation period of the detectors central frequency. On a first glance this is also the most contra-intuitive aspect. Vacuum fluctuation amplitude scales with the inverse of the four dimensional space-time volume over which the probe pulse detects the signal from purely virtual photons. So the shorter the probe pulse gets and the more it is focused, the higher is the obtained amplitude of vacuum fluctuations.
Obtaining surprising result is one thing, but how hard was it to convince your peers in the research community - in particular Science reviewers - that you were not just measuring another source of noise in your lab?
First of all we had to convince ourselves. We brain-stormed all sorts of different explanations and went through each and every one and it turned out that all of them could be ruled out - the only explanation that remained was that we saw the direct fluctuations of the vacuum field in our signal. What convinced us even more that the experiment agreed quantitatively with the complete quantum description we derived. Going through all those steps ourselves helped a lot to anticipate and understand the questions and arguments of our reviewers and colleagues. With the direct observation of vaccuum fluctuations and the accompanying complete quantum description we opened up the new field of time-domain quantum optics.
Will you take all that nice momentum of your recent work to continue with a career in academia?
Working on fundamental phenomena like this one opens up a lot more questions. Of course I am very interested in following up with those and try out a few of the many ideas I still have. On the other hand I am fascinated by the transfer of fundamental knowledge into real-world technology. So let's see what the future brings...
New Video: Introduction to LabOne
In our latest video Juerg Schwizer, Head of Software Development, provides a quick introduction to LabOne, the Zurich Instruments instrument control software. Juerg provides crisp answers to the questions:
- Why did we develop LabOne?
- How does LabOne work?
- Which features help solving your measurement challenges?
Software Trigger as a multichannel imaging tool
Among the massive amount of data the Zurich Instruments UHFLI lock-in amplifier can generate in a short time, one might be interested only in obtaining single pixels or lines upon triggers from a scan generator or an external spectrometer. By default, the flow of any demodulator data is set to a continuous transfer rate. For data alignment with third party instruments, especially for imaging applications, it is often preferable to define either 1 Pixel Trigger = 1 Demodulated Sample or 1 Line Trigger = 1 Set of data per line at the appropriate transfer rate on a low or high gate. This can be defined as a hardware trigger condition on a DIO input as reported in this blog post. With this approach, however, only demodulated samples and auxiliary input data with the same time stamp can be aligned and any initial or final 'glitch' in the scan line, e.g. due to coarse scanner motion, cannot be easily discarded from the recorded data.
The Software Trigger tool provided by the LabOne User Interface, now also available for all HF2LI users, allows temporal alignment of not only Demodulated Samples but also PID values, Error signals, Boxcar outputs & Arithmetic Unit values. All signal traces can be displayed in a line-by-line fashion and in real time as the scan progresses. The initial delay, also termed the pre-trigger condition, accounts for any of the glitches occurring before the actual line starts and any arbitrary duration can be set by the user corresponding to exactly one complete line. This allows recording of only the relevant data which makes artifact-free image reconstruction much easier. This blog post provides all the details on how to set up such trigger conditions in the context of laser probing applications.
Squelch for phase measurements
Determining the phase of a signal that has very low SNR, or that vanishes completely at times, introduces ugly artefacts in imaging applications and renders feedback-loop applications impossible. The phase is usually calculated from the in-phase component X and the quadrature component Y by
In particular when X gets small and toggles between positive and negative values, the resulting Theta values are distributed randomly over the entire range of ±π (or ±180, in degrees).
Wouldn't it be nice if the resulting phase could be set to zero (or any other chosen value) whenever the amplitude
of the signal is smaller than a definable threshold?
A similar functionality is widely known in the radio community as squelch, where the loudspeaker is only enabled when the signal level exceeds the adjustable squelch threshold and hence spares the users from listening to noise all the time.
Users of the Zurich Instruments UHFLI Lock-In Amplifier can implement a phase squelch with the following trick:
select R, Pre-Offset = Squelch Threshold, Gain = 10M, Low Limit = 0 V, Upper Limit = 1 V
connect Auxiliary Output 4 to Auxiliary Input 1
Phase(Demod 1) * Auxiliary Input 1
Select AU as output, adjust scaling and offsets
Step 1 forces the voltage of Auxiliary Output 4 to toggle between 0 (R lower than threshold) and 1 (R higher than threshold) which is then multiplied with the phase in step 3, effectively making it equal to 0 below threshold and leaving it unaffected above it.
Playing with the Pre-Offset of Auxiliary Output 4 allows you to set the appropriate squelch threshold for the application. Auxiliary Output 1 Pre-Offset and Offset can help to derive a non-zero phase signal at sub-threshold times.