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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 19, Iss. 3 — Jan. 31, 2011
  • pp: 2079–2084
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Optoelectronic detection of millimetre-wave signals with travelling-wave uni-travelling carrier photodiodes

Efthymios Rouvalis, Martyn J. Fice, Cyril C. Renaud, and Alwyn J. Seeds  »View Author Affiliations


Optics Express, Vol. 19, Issue 3, pp. 2079-2084 (2011)
http://dx.doi.org/10.1364/OE.19.002079


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Abstract

Optically pumped mixing in travelling-wave uni-travelling carrier photodiodes is proposed as a novel technique for detecting millimetre-wave signals. An experimental demonstration was performed at a frequency of 100 GHz. From DC measurements, an increase in the responsivity was found at high levels of optical power. The mixing mechanism is attributed to the variation of the responsivity with the applied reverse bias and the optical input power. The maximum intermediate frequency power was found to be −35 dBm for a 4 dBm radio frequency power, while an average conversion loss of 40 dB was achieved. A wide dynamic range of more than 42 dB was measured, limited by the maximum available millimetre-wave power.

© 2011 OSA

1. Introduction

In this paper we investigate the capability of the Travelling-Wave Uni-Travelling Carrier Photodiode (TW-UTC-PD), originally studied in [12

12. E. Rouvalis, C. C. Renaud, D. G. Moodie, M. J. Robertson, and A. J. Seeds, “Traveling-wave Uni-Traveling Carrier photodiodes for continuous wave THz generation,” Opt. Express 18(11), 11105–11110 (2010). [CrossRef] [PubMed]

], [13

13. C. C. Renaud, M. Robertson, D. Rogers, R. Firth, P. J. Cannard, R. Moore, and A. J. Seeds, “A high responsivity, broadband waveguide uni-traveling carrier photodiode,” Proc. SPIE 6194, 61940C, 61940C-8 (2006). [CrossRef]

] for efficient photonic THz generation, for down-conversion of THz signals with an optically supplied LO signal– an Optically Pumped Mixer (OPM) [14

14. N. J. Gomes and A. J. Seeds, “Novel optically pumped electronic mixer using a Mott diode structure,” Electron. Lett. 23(20), 1084–1085 (1987). [CrossRef]

]. Previously demonstrated coherent detection schemes were either based on photoconductive techniques [15

15. S. Verghese, K. A. McIntosh, S. Calawa, W. F. Dinatale, E. K. Duerr, and K. A. Molvar, “Generation and detection of coherent terahertz waves using two photomixers,” Appl. Phys. Lett. 73(26), 3824–3826 (1998). [CrossRef]

], [16

16. B. Sartorius, M. Schlak, D. Stanze, H. Roehle, H. Künzel, D. Schmidt, H.-G. Bach, R. Kunkel, and M. Schell, “Continuous wave terahertz systems exploiting 1.5 µm telecom technologies,” Opt. Express 17(17), 15001–15007 (2009). [CrossRef] [PubMed]

] or on homodyne detection [17

17. T. Nagatsuma, A. Kaino, S. Hisatake, K. Ajito, H.-J. Song, A. Wakatsuki, Y. Muramoto, N. Kukutsu, and Y. Kado, “Continuous-wave Terahertz Spectroscopy System Based on Photodiodes,” PIERS Online 6(4), 390–394 (2010). [CrossRef]

]. Both functions of generating the LO and mixing are implemented in a standalone, room-temperature, InP-based device. A first set of OPM experiments was performed at a frequency of 100 GHz and the results of the different experiments are presented in this paper. The purpose of this work was to investigate the effect of the variation of different parameters on the performance of the mixer. For this set of experiments the LO is photonically generated and the incoming signal to be down-converted is in the millimetre-wave range. By definition, in a mixer the power of the Radio Frequency (RF) signal is substantially lower than the LO power. However, for the measurements that will follow this is not always the case. One of the most important parameters of an OPM is the Conversion Loss (CL). In this paper the CL will be defined as the ratio CL = PIF/PRF where PIF is the calibrated power of the Intermediate Frequency (IF) signal and PRF the calibrated power of the RF signal. All the experiments were performed at an LO frequency, fLO, of 100 GHz. The mixing mechanism can be explained by the introduction of the differential conductance GD in the I-V characteristic of the device that is a function of the applied reverse bias and the optical power. At large reverse bias and low optical powers GD takes small values. However, we found that when the optical power is increased GD is considerable even for high levels of reverse bias (>2.5 V) voltage where the device frequency response is optimum. It was experimentally verified that the lowest CL was obtained for the highest photocurrent at the maximum reverse bias of 4 V. This is of high importance for the development of a broadband THz photomixing receiver since the frequency response of the photogenerated LO will be optimum. Finally, a very wide dynamic range of 42 dB was measured limited by the available THz power.

2. Experimental arrangement

For a given device, CL is a function of several parameters such as the frequency of the LO, fLO, the DC photocurrent, Iph, the applied reverse bias, Vb, the input optical power, Popt, the DC responsivity of the device, R, the power of the RF signal, PRF, the IF, fIF, and many other parameters. To simplify the process, several of the above parameters were kept constant. The full experimental arrangement for this series of measurements can be seen in Fig. 1
Fig. 1 Experimental Arrangement used for Optoelectronic Mixing experiments at 100 GHz.
:

An optical LO was generated by Optically Injection Locking (OIL) two widely tuneable slave lasers to a comb generated by a phase modulator. The Seed Laser wavelength was at 1531 nm and the phase modulator was driven with a 20 GHz signal. This allowed for the two slave lasers to be locked at a spacing of 100 GHz. A W-Band (75-110 GHz) × 6 frequency multiplier was used as the RF source, pumped by a signal generator. The experiments were performed on a Coplanar Waveguide (CPW)-integrated device with the same epitaxial structure as the type 1 devices in [12

12. E. Rouvalis, C. C. Renaud, D. G. Moodie, M. J. Robertson, and A. J. Seeds, “Traveling-wave Uni-Traveling Carrier photodiodes for continuous wave THz generation,” Opt. Express 18(11), 11105–11110 (2010). [CrossRef] [PubMed]

] and an active area of 4 × 25 μm2. A W-Band coplanar probe was used to feed the RF signal into the device and to extract the IF. The RF signal from the multiplier was fed into the photodiode through a free space path employing two 20 dBi gain W-Band horn antennas. The IF signal was extracted from the DC port of the internal bias-tee of the probe. A second external bias-tee was used to split the DC bias from the IF signal and the IF signal level was measured with a spectrum analyser. It was found from the experiment that the RF and the IF signals experience some losses. Some essential calibrations were performed before as part of the measurement procedure. Since the output power of the multiplier is a function of the input power, the output power was measured with a power meter and a spectrum analyser that employed a down-converting mixer. It was experimentally verified that the output power PRF increases with (PRF in)6 for input power levels up to −4 dBm, with (PRF in)4 from −4 dBm to −1 dBm and shows saturating behaviour above −1 dBm. The total loss for the RF signal was found to be 2.7 dB for frequencies around 100 GHz and depended mostly on the insertion loss of the equipment used. Another set of calibrations was performed for the IF signal. As previously mentioned, the IF signal was extracted from the DC port of the built-in bias-tee of the W-Band probe, thus the IF signal is measured after passing through a low pass (probe) and a high pass (bias-tee) filter. The IF bandwidth, measured by sweeping the RF frequency, was found to be 60 kHz, centred on 50 kHz. This was confirmed by measuring the response of the IF path when a swept-frequency amplitude modulated optical signal was input to the photodiode. A minimum total loss of 5 dB was obtained at 50 kHz, and hence this frequency was used as the IF for all measurements. The results presented in this paper are calibrated to the measured insertion loss for both the IF and the RF signals. The narrow IF bandwidth is determined by the combination of the high- and low-pass frequency responses of the two bias tees in the IF path. By improving the method of extracting the IF from the photodiode, an IF bandwidth of several GHz should be achievable.

3. Results and discussion

Some initial measurements were taken to ensure the quality of beat signal generated with OIL. The resulting signal that corresponded to the LO was found to be stable enough to perform mixing measurements with a variation of ± 1 dB. From this set of measurements, it was found that the drop in the response of the photodiode relative to low frequencies at 100 GHz was 8 dB, while a 3-dB bandwidth of 63 GHz was measured with the same optical heterodyne system. These values were confirmed with measurements taken with a power meter. The lower 3-dB bandwidth resulted from the larger active area (4 × 25 μm2) of the device compared to those reported in [12

12. E. Rouvalis, C. C. Renaud, D. G. Moodie, M. J. Robertson, and A. J. Seeds, “Traveling-wave Uni-Traveling Carrier photodiodes for continuous wave THz generation,” Opt. Express 18(11), 11105–11110 (2010). [CrossRef] [PubMed]

]. The first set of measurements involved the static I-V characteristics of the device. The DC photocurrent was measured at a wavelength of 1531 nm, the central wavelength used for these measurements. The I-V curves for various levels of input optical power are plotted in Fig. 2
Fig. 2 DC Photocurrent versus reverse bias for various levels of optical input power.
:

For low optical input powers, the IF power shows a maximum at a relatively low bias (typically about 1-1.5 V reverse bias) and then drops smoothly for higher levels of bias. As the photocurrent increases, this point is shifted to a higher reverse bias but a second overall maximum is obtained at the maximum applied reverse bias of 4 V. At a maximum photocurrent of 7 mA and a bias of 4 V, the highest IF power is obtained, that is −35 dBm. The mixing effects can be explained by incorporating the change of GD for a certain level of bias that is a figure of merit of the associated nonlinearity. The generated photocurrent without the presence of the RF signal consists of DC and AC components. At a low bias GD takes large values but the AC photocurrent is very small. When the bias is increased, the LO generated power increases substantially and a difference of about 25 dB is measured on a 50 Ω load when the reverse bias voltage changes from 1.5 V to 4 V. At the point where the maximum IF power was detected the device shows a considerable value of GD together with a high AC photocurrent. The modulation of the bias voltage by the LO signal in turn modulates the total photocurrent. The result of this modulation on the photocurrent is believed to be the main mixing mechanism.

The noise performance of the optoelectronic mixer was also assessed. At an Iph of 7 mA and a Vb of 4 V, the IF noise floor was found to be −104.1 dBm/Hz. This value was determined by the measured noise floor calibrated to the non-ideal response of the input filter and the logarithmic gain shape of the input amplifier of the spectrum analyser. This noise floor was found to be associated with the ASE noise from the EDFA that was used to amplify the LO signal and is not down-converted from the millimetre-wave regime. By removing the incoming RF signal from the input port of the mixer, the IF noise floor was not altered indicating that the IF noise floor was caused by the photonic LO.

4. Conclusion

Acknowledgements

This work was supported by the PORTRAIT (EP/D502233/1) and PHITSIN (EP/E027520/1) Engineering and Physical Science Research Council grants and by the Air Force Office of Scientific Research, Air Force Material Command, USAF (grant number FA8655-09-1-3078).

References and links

1.

P. H. Siegel, “Terahertz Technology,” IEEE Trans. Microw. Theory Tech. 50(3), 910–928 (2002). [CrossRef]

2.

M. Tonouchi, “Cutting edge terahertz technology,” Nat. Photonics 1(2), 97–105 (2007). [CrossRef]

3.

N. Karpowicz, H. Zhong, J. Xu, K.-I. Lin, J.-S. Hwang, and X.-C. Zhang, “Comparison between pulsed terahertz time-domain imaging and continuous wave terahertz imaging,” Semicond. Sci. Technol. 20(7), S293–S299 (2005). [CrossRef]

4.

H.-W. Hübers, “Terahertz Heterodyne Receivers,” IEEE J. Sel. Top. Quantum Electron. 14(2), 378–391 (2008). [CrossRef]

5.

S. Verghese, E. K. Duerr, K. A. McIntosh, S. M. Duffy, S. D. Calawa, C.-Y. E. Tong, R. Kimberk, and R. Blundell, “A photomixer local oscillator for a 630-GHz heterodyne receiver,” IEEE Microw. Guided Wave Lett. 9(6), 245–247 (1999). [CrossRef]

6.

I. Cámara Mayorga, P. M. Pradas, M. Mikulics, A. Schmitz, P. van der Wal, C. Kasemann, R. Güsten, K. Jacobs, M. Marso, H. Lüth, and P. Kordoš, “Terahertz photonic mixers as local oscillators for hot electron bolometer and superconductor-insulator-superconductor astronomical receivers,” J. Appl. Phys. 100(4), 043116 (2006). [CrossRef]

7.

S. Kohjiro, K. Kikuchi, M. Maezawa, T. Furuta, A. Wakatsuki, H. Ito, N. Shimizu, T. Nagatsuma, and Y. Kado, “A 0.2–0.5 THz single-band heterodyne receiver based on a photonic local oscillator and a superconductor-insulator-superconductor mixer,” Appl. Phys. Lett. 93(9), 093508 (2008). [CrossRef]

8.

M. C. Wanke, E. W. Young, C. D. Nordquist, M. J. Cich, A. D. Grine, C. T. Fuller, J. L. Reno, and M. Lee, “Monolithically integrated solid-state terahertz transceivers,” Nat. Photonics 4(8), 565–569 (2010). [CrossRef]

9.

M. Tsuchiya and T. Hoshida, “Nonlinear Photodetection Scheme and Its System Applications to Fiber-Optic Millimeter-Wave Wireless Down-Links,” IEEE Trans. Microw. Theory Tech. 47(7), 1342–1350 (1999). [CrossRef]

10.

J.-W. Shi, Y.-S. Wu, and Y.-S. Lin, “Near-Ballistic Uni-Traveling-Carrier Photodiode- Based V-Band Optoelectronic Mixers with Internal up-Conversion-Gain, Wide Modulation Bandwidth, and Very High Operation Current Performance,” IEEE Photon. Technol. Lett. 20(11), 939–941 (2008). [CrossRef]

11.

H. Pan, Z. Li, and J. C. Campbell, “High-Power High-Responsivity Modified Uni-Traveling-Carrier Photodiode Used as V-Band Optoelectronic mixer,” J. Lightwave Technol. 28(8), 1184–1189 (2010). [CrossRef]

12.

E. Rouvalis, C. C. Renaud, D. G. Moodie, M. J. Robertson, and A. J. Seeds, “Traveling-wave Uni-Traveling Carrier photodiodes for continuous wave THz generation,” Opt. Express 18(11), 11105–11110 (2010). [CrossRef] [PubMed]

13.

C. C. Renaud, M. Robertson, D. Rogers, R. Firth, P. J. Cannard, R. Moore, and A. J. Seeds, “A high responsivity, broadband waveguide uni-traveling carrier photodiode,” Proc. SPIE 6194, 61940C, 61940C-8 (2006). [CrossRef]

14.

N. J. Gomes and A. J. Seeds, “Novel optically pumped electronic mixer using a Mott diode structure,” Electron. Lett. 23(20), 1084–1085 (1987). [CrossRef]

15.

S. Verghese, K. A. McIntosh, S. Calawa, W. F. Dinatale, E. K. Duerr, and K. A. Molvar, “Generation and detection of coherent terahertz waves using two photomixers,” Appl. Phys. Lett. 73(26), 3824–3826 (1998). [CrossRef]

16.

B. Sartorius, M. Schlak, D. Stanze, H. Roehle, H. Künzel, D. Schmidt, H.-G. Bach, R. Kunkel, and M. Schell, “Continuous wave terahertz systems exploiting 1.5 µm telecom technologies,” Opt. Express 17(17), 15001–15007 (2009). [CrossRef] [PubMed]

17.

T. Nagatsuma, A. Kaino, S. Hisatake, K. Ajito, H.-J. Song, A. Wakatsuki, Y. Muramoto, N. Kukutsu, and Y. Kado, “Continuous-wave Terahertz Spectroscopy System Based on Photodiodes,” PIERS Online 6(4), 390–394 (2010). [CrossRef]

18.

C. C. Renaud, L. Ponnampalam, F. Pozzi, E. Rouvalis, D. Moodie, M. Robertson, and A. J. Seeds, “Photonically Enabled Communication Systems Beyond 1000 GHz,” International Topical Meeting on Microwave Photonics2008(MWP 2008), (Gold Coast, Australia), pp. 55–58.

OCIS Codes
(040.0040) Detectors : Detectors
(040.2840) Detectors : Heterodyne
(040.5160) Detectors : Photodetectors
(250.0250) Optoelectronics : Optoelectronics

ToC Category:
Detectors

History
Original Manuscript: December 2, 2010
Revised Manuscript: January 13, 2011
Manuscript Accepted: January 13, 2011
Published: January 19, 2011

Citation
Efthymios Rouvalis, Martyn J. Fice, Cyril C. Renaud, and Alwyn J. Seeds, "Optoelectronic detection of millimetre-wave signals with travelling-wave uni-travelling carrier photodiodes," Opt. Express 19, 2079-2084 (2011)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-3-2079


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References

  1. P. H. Siegel, “Terahertz Technology,” IEEE Trans. Microw. Theory Tech. 50(3), 910–928 (2002). [CrossRef]
  2. M. Tonouchi, “Cutting edge terahertz technology,” Nat. Photonics 1(2), 97–105 (2007). [CrossRef]
  3. N. Karpowicz, H. Zhong, J. Xu, K.-I. Lin, J.-S. Hwang, and X.-C. Zhang, “Comparison between pulsed terahertz time-domain imaging and continuous wave terahertz imaging,” Semicond. Sci. Technol. 20(7), S293–S299 (2005). [CrossRef]
  4. H.-W. Hübers, “Terahertz Heterodyne Receivers,” IEEE J. Sel. Top. Quantum Electron. 14(2), 378–391 (2008). [CrossRef]
  5. S. Verghese, E. K. Duerr, K. A. McIntosh, S. M. Duffy, S. D. Calawa, C.-Y. E. Tong, R. Kimberk, and R. Blundell, “A photomixer local oscillator for a 630-GHz heterodyne receiver,” IEEE Microw. Guided Wave Lett. 9(6), 245–247 (1999). [CrossRef]
  6. I. Cámara Mayorga, P. M. Pradas, M. Mikulics, A. Schmitz, P. van der Wal, C. Kasemann, R. Güsten, K. Jacobs, M. Marso, H. Lüth, and P. Kordoš, “Terahertz photonic mixers as local oscillators for hot electron bolometer and superconductor-insulator-superconductor astronomical receivers,” J. Appl. Phys. 100(4), 043116 (2006). [CrossRef]
  7. S. Kohjiro, K. Kikuchi, M. Maezawa, T. Furuta, A. Wakatsuki, H. Ito, N. Shimizu, T. Nagatsuma, and Y. Kado, “A 0.2–0.5 THz single-band heterodyne receiver based on a photonic local oscillator and a superconductor-insulator-superconductor mixer,” Appl. Phys. Lett. 93(9), 093508 (2008). [CrossRef]
  8. M. C. Wanke, E. W. Young, C. D. Nordquist, M. J. Cich, A. D. Grine, C. T. Fuller, J. L. Reno, and M. Lee, “Monolithically integrated solid-state terahertz transceivers,” Nat. Photonics 4(8), 565–569 (2010). [CrossRef]
  9. M. Tsuchiya and T. Hoshida, “Nonlinear Photodetection Scheme and Its System Applications to Fiber-Optic Millimeter-Wave Wireless Down-Links,” IEEE Trans. Microw. Theory Tech. 47(7), 1342–1350 (1999). [CrossRef]
  10. J.-W. Shi, Y.-S. Wu, and Y.-S. Lin, “Near-Ballistic Uni-Traveling-Carrier Photodiode- Based V-Band Optoelectronic Mixers with Internal up-Conversion-Gain, Wide Modulation Bandwidth, and Very High Operation Current Performance,” IEEE Photon. Technol. Lett. 20(11), 939–941 (2008). [CrossRef]
  11. H. Pan, Z. Li, and J. C. Campbell, “High-Power High-Responsivity Modified Uni-Traveling-Carrier Photodiode Used as V-Band Optoelectronic mixer,” J. Lightwave Technol. 28(8), 1184–1189 (2010). [CrossRef]
  12. E. Rouvalis, C. C. Renaud, D. G. Moodie, M. J. Robertson, and A. J. Seeds, “Traveling-wave Uni-Traveling Carrier photodiodes for continuous wave THz generation,” Opt. Express 18(11), 11105–11110 (2010). [CrossRef] [PubMed]
  13. C. C. Renaud, M. Robertson, D. Rogers, R. Firth, P. J. Cannard, R. Moore, and A. J. Seeds, “A high responsivity, broadband waveguide uni-traveling carrier photodiode,” Proc. SPIE 6194, 61940C, 61940C-8 (2006). [CrossRef]
  14. N. J. Gomes and A. J. Seeds, “Novel optically pumped electronic mixer using a Mott diode structure,” Electron. Lett. 23(20), 1084–1085 (1987). [CrossRef]
  15. S. Verghese, K. A. McIntosh, S. Calawa, W. F. Dinatale, E. K. Duerr, and K. A. Molvar, “Generation and detection of coherent terahertz waves using two photomixers,” Appl. Phys. Lett. 73(26), 3824–3826 (1998). [CrossRef]
  16. B. Sartorius, M. Schlak, D. Stanze, H. Roehle, H. Künzel, D. Schmidt, H.-G. Bach, R. Kunkel, and M. Schell, “Continuous wave terahertz systems exploiting 1.5 µm telecom technologies,” Opt. Express 17(17), 15001–15007 (2009). [CrossRef] [PubMed]
  17. T. Nagatsuma, A. Kaino, S. Hisatake, K. Ajito, H.-J. Song, A. Wakatsuki, Y. Muramoto, N. Kukutsu, and Y. Kado, “Continuous-wave Terahertz Spectroscopy System Based on Photodiodes,” PIERS Online 6(4), 390–394 (2010). [CrossRef]
  18. C. C. Renaud, L. Ponnampalam, F. Pozzi, E. Rouvalis, D. Moodie, M. Robertson, and A. J. Seeds, “Photonically Enabled Communication Systems Beyond 1000 GHz,” International Topical Meeting on Microwave Photonics2008(MWP 2008), (Gold Coast, Australia), pp. 55–58.

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