2021 Fiscal Year Research-status Report
Novel Method to Measure the Gravitational Constant
| Project/Area Number |
21K03603
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| Research Institution | Rikkyo University |
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Principal Investigator |
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| Project Period (FY) |
2021-04-01 – 2023-03-31
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| Keywords | Interferometer / Mach-Zehnder / Laser |
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| Outline of Annual Research Achievements |
During this fiscal year, I have used the dedicated Kiban-C budget to purchase optics to set up a polarization interferometer which I have used to study the polarization stability of the frequency-stabilized laser, which has been purchased as well as one of the core elements of my project. I could show that the laser is polarization stable down to mrad which was one of the key-features to be shown.
In addition, a Mach-Zehnder Interferometer has been build and tested in form of a heterodyne detector for weak oscillations of a test-mirror connected to a Piezo-osillator. With this setup and by using a HeNe-laser (different to the frequency-stabilized one), I could show its effectivity as a Doppler-Interferometer by detecting oscillation amplitudes of ~70pm.
I have done comprehensive simulation on the effects of gravity on a laser and concluded slight changes in my future research plan. Instead of a microlense-array, a frequency-modulated laser shall be used as input-field for the cavities. With such an input, the reflecting and interfering fields can be treated as Doppler-shifted and detected with the above mentioned heterodyne detector.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
Within the set schedule, I could purchase all necessary parts and perform the initial setups and measurements as planned. In addition, I could reconsider the setup to become more effective for the measurements to come.
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| Strategy for Future Research Activity |
As mentioned in the report, the original plan will slightly change from a Michelson Interferometer (IF) with microlense-array towards a Michelson IF with frequency-modulated laser (FML) and heterodyne detector. This scheme has several benefits: 1) polarization stable, as optics like lenses tend to change polarization depending on material and stress. 2) increased sensitivity due to frequency-modulation which is immune against amplitude noise.
As a consequence, the schedule will be adjusted as follows. Within the next fiscal year, the Michelson IF (without Fabry-Perot cavities) will be build and adjusted to work with a FML which is realized by using the frequency-stabilized laser purchased in 2021 and an electro-optical modulator (EOM). The second milestone during 2022 is then to connect this IF setup with the heterodyne detector constructed in 2021.
In parallel, a journal paper is prepared to summarize the considerations and give first impressions on the sensitivity of the instrument.
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| Causes of Carryover |
Use incurring amount as follows together with the budget for next year.
As written in the research plan for the next FY, a Michelson IF with FML is to be build. For this setup, dielectric high-reflectivity mirrors for the MIchelson IF are needed in addition to optics for using the frequency-stabilized laser as input source.
In order to modulate this laser into a FML, an electro-optical modulator (EOM) plus amplifier equipment is needed which will use most of the funds for the next FY (expected: ~800.000\). Together with the auxiliary optical and mechanical components (lenses, holders, posts, etc.), 1.400.000\ are expected to be used up fully.
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