An Electrically Driven, Ultrahigh-Speed, on-Chip Light Emitter Based on Carbon Nanotubes

Abstract

The integration of high-speed light emitters on silicon chips is an important issue that must be resolved in order to realize on-chip or interchip optical interconnects. Here, we demonstrate the first electrically driven ultrafast carbon nanotube (CNT) light emitter based on blackbody radiation with a response speed (1-10 Gbps) that is more than 10(6) times higher than that of conventional incandescent emitters and is either higher than or comparable to that of light-emitting diodes or laser diodes. This high-speed response is explained by the extremely fast temperature response of the CNT film, which is dominated by the small heat capacity of the CNT film and its high heat dissipation to the substrate. Moreover, we experimentally demonstrate 140 ps width pulsed light generation and real-time optical communication. This CNT-based emitter with the advantages of ultrafast response speeds, a small footprint, and integration on silicon can enable novel architectures for optical interconnects, photonic, and optoelectronic integrated circuits.

Sub-nanosecond light-pulse generation with waveguide-coupled carbon nanotube transducers

“…Upon switching the electrical signal on and off, we observe a fast initial response on a sub-nanosecond timescale, followed by an additional slower response on the scale of 10–100 ns. A similar behavior has been observed with electrically biased SWCNT films and was attributed to fast heating of SWCNTs and slow heating of the substrate [11]. We believe that this interpretation holds also for the response of our WG-CNT transducers.…”

“…In theory, the characteristic timescale of a thermal emitter τ therm solely depends on the mass density ρ CNT , the specific heat capacitance c CNT , and thermal conductance g between the CNTs and the substrate, as pointed out previously [11,19]: τ therm = ρ CNT · c CNT / g . For our CNTs with a diameter of 0.8–1.2 nm at 1000–1500 K, ρ CNT varies between 0.7·10 −15 and 1.8·10 −15 kg/m, g is in the range of 0.1–0.3 W/K·m [19] and c CNT = 2500–3900 Ws/kg·K [24].…”

“…Beyond continuous wave generation of light, an important aspect that needs to be addressed is the question of how fast a waveguide-coupled CNT transducer can respond to an electrical signal. Indeed, time-dependent incandescence from a CNT film in free-space has been measured [11] and modulation of CNT emission with decay times below 250 ps has been shown [6]. The intrinsic characteristic timescale for CNT incandescence is expected to be of the order of 10 ps, estimated from the heat capacitance of the CNTs and the thermal coupling to the dielectric substrate and metallic leads [11].…”

“…Indeed, time-dependent incandescence from a CNT film in free-space has been measured [11] and modulation of CNT emission with decay times below 250 ps has been shown [6]. The intrinsic characteristic timescale for CNT incandescence is expected to be of the order of 10 ps, estimated from the heat capacitance of the CNTs and the thermal coupling to the dielectric substrate and metallic leads [11]. Hence, CNT-based transducers operating at 100 GHz seem to be possible.…”

Tunable electronic correlation effects in nanotube-light interactions

“…Nanotubes thus offer an ideal platform for the fundamental studies of the many-body interactions and their impact on the optical spectra of photoexcited quasi-1D systems [2][3][4][5][6][7][8][9]. Knowledge of the underlying optical response of nanotubes under carrier doping is also of great importance for the * miyauchi@iae.kyoto-u.ac.jp † tony.heinz@columbia.edu development of electrically tunable optoelectronic devices [11][12][13]56,59] that operate at room temperature and on the nanometer length scale. For a complete understanding of the impact of many-body electronic correlation effects on the optical response, it is highly desirable to observe broadband optical response of clean and isolated 1D nanostructures over a wide range of free-carrier densities.…”