Highlighted Publications

Pseudo-magnetic field-induced slow carrier dynamics in periodically strained graphene, Nature Communications (2021) [PDF]

The creation of pseudo-magnetic fields in strained graphene has emerged as a promising route to allow observing intriguing physical phenomena that would be unattainable with laboratory superconducting magnets. In this work, using time-resolved infrared pump-probe spectroscopy, we provide unambiguous evidence for slow carrier dynamics enabled by giant pseudo-magnetic fields in periodically strained graphene. 

‌‌Click HERE to see the article covered by Optics & Photonics News.

Low-threshold optically pumped lasing in highly strained Ge nanowires, Nature Communications ‌(2017) [PDF]

The integration of efficient, miniaturized group IV lasers into CMOS architecture holds the key to the realization of fully functional photonic-integrated circuits. In this work, we demonstrate a low-threshold, compact group IV laser that employs a germanium nanowire under a 1.6% uniaxial tensile strain as the gain medium. 
‌Click HERE to see the article covered by Laser Focus World. 

All Publications

Note 1: Asterisk (*) denotes corresponding author.
Note 2: Dagger (†) denotes equal contributions.

2022

54. J. Tan, ..., D. Nam*, ‌‌“Ion-implantation-enabled tensile strain engineering in Ge-on-insulator (GOI) devices,” In Preparation

53. J. Tan†, D. Burt†, ..., D. Nam*, ‌‌“GeSn-on-lithium niobate-on-insulator (GeSn-LNOI) for realizing integrated nonlinear optical devices,” In Preparation

52. H. Joo†, M. Chen†, ..., D. Nam*, ‌‌“Highly sensitive mid-infrared photodetection in GeSn suspended 1D photonic crystal lasers with ultra-high temperature sensitivity,” In Preparation

51. H. Joo†, M. Chen†, ..., D. Nam*, ‌‌“Localized heating-enabled highly tunable single-mode lasing in suspended GeSn 1D photonic crystal lasers,” In Preparation

50. Y. Yi†, Y. Wang†, ...,  and D. Nam*, ‌‌“Strongly localized and tunable strain in 2D materials towards developing indistinguishable single-photon sources, In Preparation

49. H. Joo†, J. Liu†, ..., C. Sirtori*, Y. Todorov*, and D. Nam*, ‌‌“Electrically tunable single-mode lasing in high-Q optomechanical GeSn resonators, In Preparation

48. H. Joo†, Y. Kim†, ...,  and D. Nam*, ‌‌“1D photonic crystal GeSn nanobeam lasers under a uniform tensile strain enabled by all-around atomic-layer deposition, In Preparation

47. B. Son†, Y. Wang†, ..., and D. Nam*, ‌‌“Two-photon absorption-based two-dimensional (2D) lateral heterostructure avalanche photodetectors, In Preparation

46. M. Atalla†, Y. Kim†, ..., D. Nam*, and O. Moutanabbir*, ‌‌“Strong electroluminescence from GeSn vertical p-i-n heterostructures,” In Preparation

45. Y. Kim†, H. Joo†, ...,  and D. Nam*, ‌‌“Dynamically tunable GeSn lasers via localized laser annealing, In Preparation

44. K. Lu†, M. Luo†, ...,  H. Sun*, and D. Nam*, ‌‌“Strong and polarized second-harmonic generation in graphene enabled by resonant optical transitions between pseudo-Landau levels, In Preparation

43. Y. Kim†, S. Assali†, ..., D. Nam*, and O. Moutanabbir*, ‌‌“Observation of strong cavity resonances in a single GeSn nanowire grown by bottom-up synthesis, In Preparation

42. K. Lu, Y. Wang, M. Luo, B. Son, Y. Yu, and D. Nam*, ‌‌“Ultrafast photoluminescence at telecom wavelengths from wafer-scale monolayer graphene enabled by Fabry-Perot interferences,” Optics Letters, Under Review

41. D. Burt†, L. Zhang†, Y. Jung, H. Joo, Y. Kim, M. Chen, B. Son, W. Fan, Z. Ikonic, C. Tan, and D. Nam*, ‌‌“Tensile strained direct bandgap GeSn microbridges enabled in GeSnOI substrates with residual tensile strain,” Applied Physics Letters, Under Review

40. Y. Wang†, D. Burt†, K. Lu, and D. Nam*, ‌‌“Second-harmonic generation in germanium-on-insulator from visible to telecom wavelengths,” Applied Physics Letters 120, 242105 (2022) [PDF]

39. D. Burt†, H. Joo†, Y. Kim†, Y. Jung, M. Chen, M. Luo, S. Parluhutan, D. Kang, S. Assali, L. Zhang, B. Son, C. Tan, O. Moutanabbir, Z. Ikonic, Y. Huang, and D. Nam*, ‌‌“Direct bandgap GeSn nanowires enabled with ultrahigh tension from harnessing intrinsic compressive strain,” Applied Physics Letters 120, 202103 (2022) [PDF]
Selected as an Editor's Pick

38. Y. Jung†, D. Burt†, Y. Kim, H. Joo, M. Chen, L. Zhang, C. Tan, and D. Nam*, ‌‌“Optically pumped low-threshold microdisk lasers in GeSn-on-insulator with reduced defect density,” Photonics Research 10, 06001332 (2022) [PDF]

37. M. Luo†, H. Sun†, Z. Qi, K. Lu, M. Chen, D. Kang, Y. Kim, D. Burt, X. Yu, C. Wang, Y. Kim, H. Wang, Q. Wang, and D. Nam*, ‌‌“Triaxially strained suspended graphene for large-area uniform pseudo-magnetic fields," Optics Letters 47, 2174-2177 (2022) [PDF] 

2021

36. Y. Kim†, S. Assali†, D. Burt, Y. Jung, H. Joo, M. Chen, D. Kang, Z. Ikonic, O. Moutanabbir* and D. Nam*, “Enhanced GeSn microdisk lasers directly released on Si," Advanced Optical Materials 9, 2101213 (2022) [PDF]

35. H. Joo†, Y. Kim†, D. Burt, Y. Jung, L. Zhang, M. Chen, S. Parluhutan, D. Kang, C. Lee, S. Assali, O. Moutanabbir, Y. Cho, C. Tan, and D. Nam*, “1D photonic crystal direct bandgap GeSn-on-insulator laser,” Applied Physics Letters 119, 201101 (2021) [PDF]

34. X. Gao†, H. Sun†, Q. Wang, and D. Nam*, ‌‌“Heterostrain‐enabled dynamically tunable moiré superlattice in twisted bilayer graphene,” Scientific Reports 11, 21402 (2021) [PDF] 

33. B. Son, L. Zhang, Y. Jung, H. Zhou, D. Nam, C. Tan, “Systematic study on photoexcited carrier dynamics related to defects in GeSn films with low Sn content at room temperature,” Semiconductor Science and Technology 36, 125018 (2021) [PDF]  

32. D. Burt†, H. Joo†, Y. Jung, Y. Kim, M. Chen, Y. Huang, and D. Nam*, “Strain-relaxed GeSn-on-insulator (GeSnOI) microdisks,” Optics Express 28, 28959-28967 (2021) [PDF] 

31. D. Kang†, H. Sun†, M. Luo†, K. Lu, M. Chen, Y. Kim, Y. Jung, X. Gao, S. Parluhutan, J. Ge, S. Koh, D. Giovanni, T. Sum, Q. Wang, H. Li, and D. Nam*, “Pseudo-magnetic field-induced slow carrier dynamics in periodically strained graphene,” Nature Communications 12, 5087 (2021) [PDF] 
Covered by Optics & Photonics NewsDong-A Ilbo, etc.

30. C. Qimiao, W. Shaoteng, Z. Lin, Z. Hao, D. Burt, D. Nam, W. Fan, and C. Tan, “GeSn-on-insulator dual-waveband resonant-cavity-enhanced photodetectors at the 2 μm and 1.55 μm optical communication bands,” Optics Letters 46, 3809-3812 (2021) [PDF] 

29. J. Ge†, B. Ding†, S. Hou†, M. Luo, D. Nam, H. Duan*, H. Gao*, Y. Lam*, and H. Li*, “Rapid fabrication of complex nanostructures using room-temperature ultrasonic nanoimprinting,” Nature Communications 12, 3146 (2021) [PDF] 

28. O. Moutanabbir*, S. Assali, X. Gong, E. O'Reilly, C. Broderick, B. Marzban, J. Witzens, W. Du, S. Yu, A. Chelnokov, D. Buca, and D. Nam, “Monolithic infrared silicon photonics: The rise of (Si)GeSn semiconductors,” Applied Physics Letters 29, 118, 110502 (2021) [PDF]  

27. Y. Jung†, Y. Kim†, D. Burt, H. Joo, D. Kang, M. Luo, M. Chen, L. Zhang, C. Tan, and D. Nam*, “Biaxially strained germanium crossbeam with high-quality optical cavity for on-chip laser applications,” Optics Express 29, 14174-14181 (2021) [PDF] 

26. H. Sun*, P. Sengupta*, D. Nam*, and B. Yang*“Negative thermal Hall conductance in two-dimer Shastry-Sutherland model with π-flux Dirac triplon,” Physical Review B 103, L140404 (2021) [PDF] 

25. H. Sun, Z. Qi, Y. Kim, M. Luo, B. Yang, and D. Nam*, “Frequency-tunable terahertz graphene laser enabled by pseudomagnetic fields in strain-engineered graphene,” Optics Express 29, 1892-1902 (2021) [PDF] 
Covered by Optics & Photonics News 

2020

24. A. Dubrovkin*, B. Qiang, T. Salim, D. Nam, N. Zheludev*, and Q.Wang*, “Resonant nanostructures for highly confined and ultra-sensitive surface phonon polaritons,” Nature Communications 11, 1863 (2020) [PDF] 

2019

23. Z. Song, W. Fan*, C. Tan, Q. Wang, D. Nam, Z. Hua, and G. Sun, “Band structure of Ge1-xSnx alloy: a full-zone 30-band k·p model,” New Journal of Physics 21, 073037 (2019) [PDF] 

2018

22. Z. Qi, H. Sun, M. Luo, Y. Jung, and D. Nam*, "Strained germanium nanowire optoelectronic devices for photonic-integrated circuits," Journal of Physics: Condensed Matter 30(33), 334004 (2018) [PDF] 

21. S. Gupta*, D. Nam, J. Vuckovic and K. Saraswat, "Room temperature lasing unraveled by a strong resonance between gain and parasitic absorption in uniaxially strained germanium," Physical Review B 97(15), 155127 (2018) [PDF] 

2017

20. S. Bao†, D. Kim†, C. Onwukaeme†, S. Gupta†, K. Saraswat, K. Lee, Y. Kim, D. Min, Y. Jung, H. Qiu, H. Wang, E. A. Fitzgerald, C. Tan* and D. Nam*, "Low-threshold optically pumped lasing in highly strained Ge nanowires," Nature Communications 8(1), 1845 (2017) [PDF] 
Covered by 
Laser Focus WorldChannel NewsAsiaetc. 

~2016 (Before Joining NTU)

19. D. Sukhdeo†, Y. Kim†, K. Saraswat, B. Dutt and D. Nam*, “Theoretical modeling for the interaction of tin alloying with n-type doping and tensile strain for GeSn lasers,” IEEE Electron Device Letters 37(10), 1307-1310 (2016) [PDF] 

18. J. Baek, B. Ki, D. Kim, C. Lee, D. Nam, Y. Cho, and J. Oh*, “Phosphorus implantation into in-situ doped Ge-on-Si for high light-emitting efficiency,” Optical Materials Express 6(9), 2939-2946 (2016) [PDF] 

17. D. Sukhdeo†, Y. Kim†, S. Gupta, K. Saraswat, B. Dutt and D. Nam*, “Anomalous threshold reduction from uniaxial strain for a low-threshold Ge laser,” Optical Communication 379, 32-35 (2016) [PDF] 

16. J. Petykiewicz†, D. Nam†, D. Sukhdeo, S. Gupta, S. Buckley, A. Piggott, J. Vučković* and K. Saraswat*, “Direct bandgap light emission from strained Ge nanowire coupled with high-Q optical cavities,” Nano Letters 16(4), 2168-2173 (2016) [PDF] 
Covered by 
Dong-A IlboDigital TimesNewsisAsia Today, etc.

15. D. Sukhdeo, S. Gupta, K. Saraswat, B. Dutt and D. Nam*, “Impact of minority carrier lifetime on the performance of strained Ge light sources,” Optical Communication 364, 233-237 (2016) [PDF] 

14. D. Sukhdeo, S. Gupta, K. Saraswat, B. Dutt and D. Nam*, “Ultimate limit of biaxial tensile strain and n-type doping for realizing an efficient low-threshold Ge laser,” Japanese Journal of Applied Physics 55, 024301 (2016) [PDF] 

13. D. Sukhdeo, J. Petykiewicz, S. Gupta, D. Kim, S. Woo, Y. Kim, J. Vučković, K. Saraswat and D. Nam*, “Ge microdisk with lithographically-tunable strain using CMOS-compatible process,” Optics Express 23(26), 33249-33254 (2015) [PDF] 

12. D. Sukhdeo, D. Nam*, J. Kang, M. Brongersma and K. Saraswat, “Bandgap-customizable germanium using lithographically determined biaxial tensile strain for silicon-compatible optoelectronics,” Optics Express 23(13), 16740-16749 (2015) [PDF] 

11. J. Nam*, F. Afshinmanesh, D. Nam, W. Jung, T. Kamins, M. Brongersma, and K. Saraswat, “Monolithic integration of germanium-on-insulator p-i-n photodetector on silicon,” Optics Express 23(12), 15816-15823 (2015) [PDF] 

10. J. Nam, S. Alkis, D. Nam, F. Afshinmanesh, J. Shim, J. Park, M. Brongersma, A. Okyay, T. Kamins and K. Saraswat*, “Lateral overgrowth for monolithic integration of germanium-on-insulator on silicon,” Journal of Crystal Growth 416, 21-27 (2015) [PDF] 

9. D. Nam*, J. Kang, M. Brongersma and K. Saraswat, “Observation of improved minority carrier lifetimes in high-quality Ge-on-insulator using time-resolved photoluminescence,” Optics Letters 39(21), 6205-6208 (2014) [PDF] 

8. D. Nam, D. Sukhdeo, S. Gupta, J. Kang, M. Brongersma and K. Saraswat, “Study of carrier statistics in uniaxially strained Ge for a low-threshold Ge laser,” IEEE Journal of Selected Topics in Quantum Electronics 20(4), 16-22 (2014) [PDF] 

7. D. Sukhdeo, D. Nam*, J. Kang, M. Brongersma and K. Saraswat, “[Invited] Direct bandgap germanium-on-silicon inferred from 5.7% uniaxial tensile strain,” Photonics Research 2(3), A8-A13 (2014) [PDF] 
Selected as #1 most cited paper during 2014-2015 & 
Awarded a Highly Cited Paper Certificate in 2019

6. B. Dutt, H. Lin, D. Sukhdeo, B. Vulovic, S. Gupta, D. Nam, K. Saraswat, and J. Harris, “theoretical analysis of GeSn alloys as a gain medium for a Si-compatible laser,” IEEE Journal of Selected Topics in Quantum Electronics 19(5), 1502706 (2013) [PDF] 

5. D. Nam, D. Sukhdeo, J. Kang, J. Petykiewicz, J. Lee, W. Jung, J. Vuckovic, M. Brongersma*, and K. Saraswat*, “Strain-induced pseudoheterostructure nanowires confining carriers at room temperature with nanoscale-tunable band profiles,” Nano Letters 13(7), 3118-3123 (2013) [PDF] 

4. B. Dutt*, D. Sukhdeo, D. Nam, B. Vulovic, Z. Yuan, and K. Saraswat, “Roadmap to an efficient germanium-on-silicon laser: strain vs. n-type doping,” IEEE Photonics Journal 4(5), 2002-2009 (2012) [PDF] 

3. W. Jung, J. Park, A. Nainani, D. Nam, and K. Saraswat, “Fluorine passivation of vacancy defects in bulk Ge metal-oxide-semiconductor field effect transistor application,” Applied Physics Letters 101(7), 072104 (2012) [PDF] 

2. D. Nam, D. Sukhdeo, S. Cheng, K. Huang, A. Roy, M. Brongersma, Y. Nishi, and K. Saraswat, “Electroluminescence from strained Ge membranes and implications for an efficient Si-compatible laser,” Applied Physics Letters 100(13), 131112 (2012) [PDF] 

1. D. Nam*, D. Sukhdeo, A. Roy, K. Balram, S. Cheng, K. Huang, Z. Yuan, M. Brongersma, Y. Nishi, D. Miller and K. Saraswat, “Strained germanium thin film membrane on silicon substrate for optoelectronics,” Optics Express 19(27), 25866-25872 (2011) [PDF] 

Patent

6. Non-Drafted Singapore Patent Application: “Biaxially strained crossbeam germanium laser structure,” D. Nam, D. Burt, Y. Jung, Y. Kim, H. Joo, Submitted on 16 Dec 2020

5. Non-Drafted Singapore Patent Application: “Graphene nanopillar structures for giant pseudo-magnetic fields,” D. Nam, D. Kang, M. Luo, H. Sun, X. Gao, K. Lu, Submitted on 15 Dec 2020

4. Non-Drafted Singapore Patent Application: “Triaxially strained graphene structure for large-area pseudo-magnetic field,” D. Nam, H. Sun, M. Luo, D. Burt, D. Kang, Submitted on 14 Dec 2020

3. Non-Drafted Singapore Patent Application, Application Number 10202012548S: “An electrically pumped strained GeSn laser structure,” D. Nam, D. Burt, Y. Jung, Y. Kim, H. Joo, Filed on 15 Dec 2020

2. Non-Drafted Singapore Patent Application, Application Number 10201806832X: “Highly strained germanium laser on a silicon platform,” D. Nam, C. Tan, Filed on 13 Aug 2018

1. US Patent No.0,372,455: “Crossed nanobeam structure for a low-threshold germanium laser,” D. Nam, J. Petykiewicz, D. Sukhdeo, S. Gupta, J. Vuckovic, K. Saraswat, Issued Sept. 9, 2015 [LINK]