Skip to main content

Low temperature microwave optomechanics: Anomalous force noise and optomechanically induced transparency

Low temperature microwave optomechanics: Anomalous force noise and optomechanically induced transparency

  • Date 10 Nov 2021
  • Time 15:00 - 16:00
  • Category Seminar

Dr. Sumit Kumar (Dept Physics, RHUL)

The mechanical properties of amorphous materials (glasses) at low temperatures are dominated by effects of low energy excitations that are thought to be atomic-scale tunneling two level systems (TTLS). In nanometerscale glass samples, the temperature dependence of the sound speed and dissipation is modified relative to that of bulk glass samples. In addition to this size effect, the usual presence of a polycrystalline metal in nanomechanical resonators leads to a further departure from the well-studied behavior of insulating bulk glass. The recent field of cavity optomechanics has paved the way for sensitive detection of the position of nanomechanical resonators and also control of its mechanical characteristics. The thermal motion measurement of 50  x 300  x 100  nanomechanical string coupled to Nb superconducting microwave cavity using cavity optomechanical techniques will be discussed. The measurement of thermal motion of the nanobeam below 𝑇 < 200 mK is marred by the anomalous force noise seen in the output power from the cavity which is not consistent with the optomechanical theory, where 𝑇 is the temperature of the sample. We will show a detailed analysis of the statistics of the anomalous force noise called “spikes” and will try to give a plausible reason for the same. Further many amplifiers and notch filters can be made from optomechanical systems. They rely on optomechanically induced transparency (OMIT) and absorption (OMIA). We will investigate our results on OMIT and OMIA covering a large parameter space than has been explored in previous works.  We then report a dual chip optomechanical measurement technique used to characterize non-metallized amorphous SiN strings at low temperatures. A harp consisting of SiN strings of width 350  and lengths 40 to 80  is coupled to an Al superconducting microwave cavity on a separate chip. The strings are driven dielectrically and their motion is detected via its modulation of the microwave resonance frequency.

Fig. caption: Dual chip cavity optomechanics: Superconducting microwave cavity chip and chip with SiN nano beam

2021 11 10 CM Seminar Sumit Kumar

Related topics

Explore Royal Holloway

Get help paying for your studies at Royal Holloway through a range of scholarships and bursaries.

There are lots of exciting ways to get involved at Royal Holloway. Discover new interests and enjoy existing ones

Heading to university is exciting. Finding the right place to live will get you off to a good start

Whether you need support with your health or practical advice on budgeting or finding part-time work, we can help

Discover more about our 21 departments and schools

Find out why Royal Holloway is in the top 25% of UK universities for research rated ‘world-leading’ or ‘internationally excellent’

Royal Holloway is a research intensive university and our academics collaborate across disciplines to achieve excellence.

Discover world-class research at Royal Holloway

Discover more about who we are today, and our vision for the future

Royal Holloway began as two pioneering colleges for the education of women in the 19th century, and their spirit lives on today

We’ve played a role in thousands of careers, some of them particularly remarkable

Find about our decision-making processes and the people who lead and manage Royal Holloway today