Periodic Reporting for period 1 - PhoSTer THz (Photonic Spectrum Analyzer for the Terahertz Spectral Domain)
Reporting period: 2022-06-01 to 2023-11-30
Scientific and commercial utilization of the Terahertz spectrum (100 GHz -10 THz) is often hindered by the lack of affordable characterization tools for developing systems towards maturity. This proposal aims for the prototype development of such tools, namely affordable spectrum analyzers (SA), in order to boost component development in the Terahertz domain (100 GHz-10THz), particularly electronic and opto-electronic components. These are employed in 6G hardware, spectroscopy including bio-medical trace gas detection, security, non-destructive testing and quality control. To date's most employed systems are electronic frequency-extended microwave SAs. Whilst very powerful, they have a few draw backs:
1.) it is very challenging to develop electronic systems for higher THz frequencies. The highest commercial frequency extension to date goes to 1.5 THz.
2.) the higher the frequency, the exponentially more expensive are the frequency extenders.
3.) The extender modules are bound to specific waveguide bands. Spectra larger than 50% of the center frequency can only be obtained by employing several extender bands.
In PhoSTer THz, we will implement a photonic spectrum analyzer system as opposed to electronic ones, with the following advantages:
1.) Spectral coverage from microwaves to several Terahertz with a single system without the need of exchanging bands.
2.) Accessing frequencies yet not accessible with commercial electronic systems
3.) Inexpensive solution: a single photonic system costs less than the electronic base unit (i.e. without extenders)
1.) it is very challenging to develop electronic systems for higher THz frequencies. The highest commercial frequency extension to date goes to 1.5 THz.
2.) the higher the frequency, the exponentially more expensive are the frequency extenders.
3.) The extender modules are bound to specific waveguide bands. Spectra larger than 50% of the center frequency can only be obtained by employing several extender bands.
In PhoSTer THz, we will implement a photonic spectrum analyzer system as opposed to electronic ones, with the following advantages:
1.) Spectral coverage from microwaves to several Terahertz with a single system without the need of exchanging bands.
2.) Accessing frequencies yet not accessible with commercial electronic systems
3.) Inexpensive solution: a single photonic system costs less than the electronic base unit (i.e. without extenders)
The photonic spectrum analyzer replaces the usually used electronic local oscillator by a photonic one. Therefore, two laser signals that differ in frequency by the desired local oscillator frequency illuminate a photoconductive material, modulating its resistance at the difference frequency, i.e. the local oscillator frequency. At the same time, the signal under test is received by an antenna attached to the photoconductive material that converts the signal to a bias. Combined with the conductance modulation by the lasers, the photoconductive material generates an intermediate frequency corresponding to the difference of local oscillator and signal frequency. By tuning the frequency of the lasers, the intermediate frequency can be chosen smaller than 1 GHz where inexpensive and effective post detection electronics exist commercially. As the signal under test and the laser beat note (i.e. the photonic local oscillator) are not phase locked, phase information cannot be recovered but the spectral power at the IF frequency can be measured in order to obtain the spectral characteristics of the source under test.
We have improved and thoroughly characterized three photonic spectrum analyzer systems and demonstrated its applications in several use cases: an inexpensive photonic spectrum analyzer that is driven by two state-of-the-art distributed feed back lasers. Its frequency coverage is solely determined by the tuning range of the lasers. The responsivity, however, rolls off towards higher frequencies. If the device under test is powerful enough, this system can work at several THz. The system is directly compatible with commercial continuous-wave homodyne THz systems with little extra effort. The main advantage of this system is the low cost. Two versions of a high performance system using optical frequency combs: The systems achieve Hz-level resolution, beyond the goal of the project. The first high performance system uses an inexpensive electro-optic continuous-wave comb system for the photonic local oscillator. The second system uses a more expensive frequency comb that offers an unprecedented tuning range. We have investigated transitions via dielectric waveguides to ground-source-ground probes in order to enable on-chip measurements of electronic THz circuits.
The scientific and technical outcomes of the project are:
-Three prototypes of free space photonic spectrum analyzers developed
-Hz-level spectral resolution achieved
-frequency coverage mainly determined by the tuning range of the laser subsystem
-GSG transitions demonstrated enabling on-chip measurements
-Several case studies carried out to demonstrate the versatility of the photonic spectrum analyzer concept
-Dissemination through one journal publication, two peer-reviewed conference proceedings
-Several presentations at conferences and potential partners for commercialization
-Two further journal publications on the high performance systems are in progress, one of them is already submitted
We have improved and thoroughly characterized three photonic spectrum analyzer systems and demonstrated its applications in several use cases: an inexpensive photonic spectrum analyzer that is driven by two state-of-the-art distributed feed back lasers. Its frequency coverage is solely determined by the tuning range of the lasers. The responsivity, however, rolls off towards higher frequencies. If the device under test is powerful enough, this system can work at several THz. The system is directly compatible with commercial continuous-wave homodyne THz systems with little extra effort. The main advantage of this system is the low cost. Two versions of a high performance system using optical frequency combs: The systems achieve Hz-level resolution, beyond the goal of the project. The first high performance system uses an inexpensive electro-optic continuous-wave comb system for the photonic local oscillator. The second system uses a more expensive frequency comb that offers an unprecedented tuning range. We have investigated transitions via dielectric waveguides to ground-source-ground probes in order to enable on-chip measurements of electronic THz circuits.
The scientific and technical outcomes of the project are:
-Three prototypes of free space photonic spectrum analyzers developed
-Hz-level spectral resolution achieved
-frequency coverage mainly determined by the tuning range of the laser subsystem
-GSG transitions demonstrated enabling on-chip measurements
-Several case studies carried out to demonstrate the versatility of the photonic spectrum analyzer concept
-Dissemination through one journal publication, two peer-reviewed conference proceedings
-Several presentations at conferences and potential partners for commercialization
-Two further journal publications on the high performance systems are in progress, one of them is already submitted
We have demonstrated that photonic systems are a viable alternative to established electronic spectrum analyzers. To our knowledge, the developed systems are the first of their kind with competitive performance. A market study has revealed that the market is currently still small, the market entrance barriers still high. The situation will alleviate in the future as the THz market grows further (~26% per year), with particular focus on the 6G wireless market and future standards where THz components will be employed. Further research, possibly involving end users and commercialization partners may be necessary in order to access the market effectively.
Overview of the results:
-Three different systems demonstrated
-Market study carried out in order to identify commercialization pathways and needs
-IP secured: a second patent application on the technology was submitted
-Dissemination: Outreach activities at conferences and trade shows
-Exploitation: Collaboration with two industrial partners for future commercialization options
Remaining needs:
-Further research and development of the prototype systems towards a product
-Access to market ideally via an established company
Overview of the results:
-Three different systems demonstrated
-Market study carried out in order to identify commercialization pathways and needs
-IP secured: a second patent application on the technology was submitted
-Dissemination: Outreach activities at conferences and trade shows
-Exploitation: Collaboration with two industrial partners for future commercialization options
Remaining needs:
-Further research and development of the prototype systems towards a product
-Access to market ideally via an established company