Limits...
Frequency-resolved optical gating measurement of ultrashort pulses by using single nanowire

View Article: PubMed Central - PubMed

ABSTRACT

The use of ultrashort pulses for fundamental studies and applications has been increasing rapidly in the past decades. Along with the development of ultrashort lasers, exploring new pulse diagnositic approaches with higher signal-to-noise ratio have attracted great scientific and technological interests. In this work, we demonstrate a simple technique of ultrashort pulses characterization with a single semiconductor nanowire. By performing a frequency-resolved optical gating method with a ZnO nanowire coupled to tapered optical microfibers, the phase and amplitude of a pulse series are extracted. The generated signals from the transverse frequency conversion process can be spatially distinguished from the input, so the signal-to-noise ratio is improved and permits lower energy pulses to be identified. Besides, since the nanometer scale of the nonlinear medium provides relaxed phase-matching constraints, a measurement of 300-nm-wide supercontinuum pulses is achieved. This system is highly compatible with standard optical fiber systems, and shows a great potential for applications such as on-chip optical communication.

No MeSH data available.


Counter-propagating pulses.(a–e) Optical microscope images of SHG with different delay in optical path. Scale bar, 50 μm. (f–j) Corresponding measured (black dots) and fitted (red line) intensity profile of (a–e).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5016840&req=5

f4: Counter-propagating pulses.(a–e) Optical microscope images of SHG with different delay in optical path. Scale bar, 50 μm. (f–j) Corresponding measured (black dots) and fitted (red line) intensity profile of (a–e).

Mentions: To verify the feasibility of using single NW for pulses characterization, we first study the pulses colliding process in the NW. Figure 4(a–e) were SH images recorded at around 405 nm during the pulse series optically gated by itself. The target pulses came from right and the gate controlled by retro-reflector came from left. It can be seen that the SH signal was first generated from left end of ZnO NW [Fig. 4(a)], become stronger with the pulses moving in [Fig. 4(b)], then reached its maximum in Fig. 4(c) and disappeared from right end of NW finally [Fig. 4(d,e)]. The corresponding position-dependent SH intensity curves of Fig. 4(a–e) were plotted in Fig. 4(f–j) in black dots by integrating the intensity of image pixels, and the Y-axis of each plot were altered to form a better contrast. The periodical pattern was originated from the guided modes of the counter-propagating waves. As proved in our previous study1314, the guided modes in NW depend on the diameter of NW, the relative position and the angle between the fiber taper and the NW. And the guided modes would further influence the SH emission. The spatial distributions in transverse SH emission are determined by the relationship of ISH ∝ cos2 (Δβz), where Δβ represents the propagation constant difference between the encountered guided modes. So the SH images of NW could manifest an oscillation behavior when Δβ ≠ 0. Nevertheless, the SH spectrum would not be influenced by the change of patterns. The red line for each panel in Fig. 4(f–j) plotted the Gaussian fitted profiles in order to make the movement of the intensity peak more obvious.


Frequency-resolved optical gating measurement of ultrashort pulses by using single nanowire
Counter-propagating pulses.(a–e) Optical microscope images of SHG with different delay in optical path. Scale bar, 50 μm. (f–j) Corresponding measured (black dots) and fitted (red line) intensity profile of (a–e).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5016840&req=5

f4: Counter-propagating pulses.(a–e) Optical microscope images of SHG with different delay in optical path. Scale bar, 50 μm. (f–j) Corresponding measured (black dots) and fitted (red line) intensity profile of (a–e).
Mentions: To verify the feasibility of using single NW for pulses characterization, we first study the pulses colliding process in the NW. Figure 4(a–e) were SH images recorded at around 405 nm during the pulse series optically gated by itself. The target pulses came from right and the gate controlled by retro-reflector came from left. It can be seen that the SH signal was first generated from left end of ZnO NW [Fig. 4(a)], become stronger with the pulses moving in [Fig. 4(b)], then reached its maximum in Fig. 4(c) and disappeared from right end of NW finally [Fig. 4(d,e)]. The corresponding position-dependent SH intensity curves of Fig. 4(a–e) were plotted in Fig. 4(f–j) in black dots by integrating the intensity of image pixels, and the Y-axis of each plot were altered to form a better contrast. The periodical pattern was originated from the guided modes of the counter-propagating waves. As proved in our previous study1314, the guided modes in NW depend on the diameter of NW, the relative position and the angle between the fiber taper and the NW. And the guided modes would further influence the SH emission. The spatial distributions in transverse SH emission are determined by the relationship of ISH ∝ cos2 (Δβz), where Δβ represents the propagation constant difference between the encountered guided modes. So the SH images of NW could manifest an oscillation behavior when Δβ ≠ 0. Nevertheless, the SH spectrum would not be influenced by the change of patterns. The red line for each panel in Fig. 4(f–j) plotted the Gaussian fitted profiles in order to make the movement of the intensity peak more obvious.

View Article: PubMed Central - PubMed

ABSTRACT

The use of ultrashort pulses for fundamental studies and applications has been increasing rapidly in the past decades. Along with the development of ultrashort lasers, exploring new pulse diagnositic approaches with higher signal-to-noise ratio have attracted great scientific and technological interests. In this work, we demonstrate a simple technique of ultrashort pulses characterization with a single semiconductor nanowire. By performing a frequency-resolved optical gating method with a ZnO nanowire coupled to tapered optical microfibers, the phase and amplitude of a pulse series are extracted. The generated signals from the transverse frequency conversion process can be spatially distinguished from the input, so the signal-to-noise ratio is improved and permits lower energy pulses to be identified. Besides, since the nanometer scale of the nonlinear medium provides relaxed phase-matching constraints, a measurement of 300-nm-wide supercontinuum pulses is achieved. This system is highly compatible with standard optical fiber systems, and shows a great potential for applications such as on-chip optical communication.

No MeSH data available.