An Overview of Terahertz Imaging with Resonant Tunneling Diodes
Round 1
Reviewer 1 Report
In the manuscript “An Overview of Terahertz Imaging with Resonant Tunneling Diodes” authors have presented an overview of the resonant tunneling diode (RTD) technology for sources and detectors of terahertz radiation.
I have a few suggestions for changes and additions before the manuscript publications in Applied Sciences.
Mentioning of Fig 2 c) is missing in the figure caption.
The device is for the terahertz range, which, “…has shorter wavelength compared with microwave and radio frequencies…”, line 26 of the manuscript. When discussed about power that can be delivered by RTD, on line 115, this is called radio frequency power. Are radio frequencies considered low frequency range of terahertz radiation?
Few sentences should be checked for English. Like “The performance of RTD and SBD detector was compared…” in line 181.
What would be square law detection on line 179? This is referenced by the book that many, me included, don’t have. I suggest an explanation what this means.
I think it should be”… in Fig. 2 (c):”, see line 177.
What is coherent in RTD coherent mode, depicted in Fig 2 c.
Unless this issue of the Applied Sciences is for experts of terahertz sources and detectors, I suggest to authors to tell us more about principle of operation of RTD as both source and detector, what might be main technological challenges, what are key parameters for RTD, why two tunneling barriers, what is causing transition from positive to negative differential resistance.
Author Response
Mentioning of Fig 2 c) is missing in the figure caption.
Caption was added for Fig. 2 (c).
The device is for the terahertz range, which, “…has shorter wavelength compared with microwave and radio frequencies…”, line 26 of the manuscript. When discussed about power that can be delivered by RTD, on line 115, this is called radio frequency power. Are radio frequencies considered low frequency range of terahertz radiation?
We have revised the sentence to make this clear.
Few sentences should be checked for English. Like “The performance of RTD and SBD detector was compared…” in line 181.
“These has been checked and revised.
What would be square law detection on line 179? This is referenced by the book that many, me included, don’t have. I suggest an explanation what this means.
We have added an explanation was added (line 193/4)
I think it should be”… in Fig. 2 (c):”, see line 177.
This typo has been corrected..
What is coherent in RTD coherent mode, depicted in Fig 2 c.
A brief explanation for this is provided (lines 214-216)
Unless this issue of the Applied Sciences is for experts of terahertz sources and detectors, I suggest to authors to tell us more about principle of operation of RTD as both source and detector, what might be main technological challenges, what are key parameters for RTD, why two tunneling barriers, what is causing transition from positive to negative differential resistance.
The principle of operation of the RTD has now been explained briefly and more clearly in section 3.
Reviewer 2 Report
The manuscript under consideration presents a brief review on resonant tunneling diode (RTD) technology application in THz imaging systems. Recent breakthroughs in source and detector devives as well as examples of their application are properly described and cited. Indeed, RTDs with their simple structure, compact size, room temperature operation and availability for coherent detection are worth candidates for near future imaging and diagnostic systems.
The mini-review can be accepted for publication in present form.
Author Response
Thanks
Reviewer 3 Report
This manuscript reviewed THz imaging systems based on room temperature transceiver technology using RTDs devices. The authors reviewed the basics of the THz imaging systems, followed by the advantages of RTDs in terms of sources and detectors. Previous work has been properly cited across the paper. The paper can be accepted for publication contingent upon the effort to address the comments below.
1. In the second paragraph of the “Introduction”, the authors should provide at least one citation for each of the following device technologies that have been used to generate THz signals: Gunn diodes, IMPATT diodes, SBDs, HEMTs, and HBTs.
2. In the 4th paragraph of “3.1 RTD device”, “the relation between the device output power with the an optimal load in an oscillator circuit was derived” should be “the relation between the device output power with an optimal load in an oscillator circuit was derived”.
3. In Conclusion, in line 10, “the advantages of RTD transceiver include simple structure, compact size…” should be revised to “the advantages of RTD source include simple structure, compact size…”.
Author Response
1. In the second paragraph of the “Introduction”, the authors should provide at least one citation for each of the following device technologies that have been used to generate THz signals: Gunn diodes, IMPATT diodes, SBDs, HEMTs, and HBTs.
References were added.
2. In the 4th paragraph of “3.1 RTD device”, “the relation between the device output power with the an optimal load in an oscillator circuit was derived” should be “the relation between the device output power with an optimal load in an oscillator circuit was derived”.
The typo has been corrected.
3. In Conclusion, in line 10, “the advantages of RTD transceiver include simple structure, compact size…” should be revised to “the advantages of RTD source include simple structure, compact size…”.
The expression of transceiver would include both source and detector.
