Applicability conditions and experimental analysis of the variable stripe length method for gain measurements

Negro, Luca Dal; Bettotti, Paolo; Cazzanelli, M.; Pacifici, Domenico; Pavesi, L.

doi:10.1016/j.optcom.2003.10.051

Cited by 139 publications

(118 citation statements)

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“…In this way this experimental set-up is usually named as variable stripe length (VSL) method, and it is commonly used to analyze active waveguides [33].…”

Section: Amplification In Colloidal Nanoparticles In Waveguides Strucmentioning

confidence: 99%

Active photonic devices based on colloidal semiconductor nanocrystals and organometallic halide perovskites

Suárez¹

2016

Eur. Phys. J. Appl. Phys.

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Abstract. Semiconductor nanocrystals have arisen as outstanding materials to develop a new generation of optoelectronic devices. Their fabrication under simple and low cost colloidal chemistry methods results in cheap nanostructures able to provide a wide range of optical functionalities. Their attractive optical properties include a high absorption cross section below the band gap, a high quantum yield emission at room temperature, or the capability of tuning the band-gap with the size or the base material. In addition, their solution process nature enables an easy integration on several substrates and photonic structures. As a consequence, these nanoparticles have been extensively proposed to develop several photonic applications, such as detection of light, optical gain, generation of light or sensing. This manuscript reviews the great effort undertaken by the scientific community to construct active photonic devices based on these nanoparticles. The conditions to demonstrate stimulated emission are carefully studied by comparing the dependence of the optical properties of the nanocrystals with their size, shape and composition. In addition, this paper describes the design of different photonic architectures (waveguides and cavities) to enhance the generation of photoluminescence, and hence to reduce the threshold of optical gain. Finally, semiconductor nanocrystals are compared to organometallic halide perovskites, as this novel material has emerged as an alternative to colloidal nanoparticles.

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“…In this way this experimental set-up is usually named as variable stripe length (VSL) method, and it is commonly used to analyze active waveguides [33].…”

Section: Amplification In Colloidal Nanoparticles In Waveguides Strucmentioning

confidence: 99%

Active photonic devices based on colloidal semiconductor nanocrystals and organometallic halide perovskites

Suárez¹

2016

Eur. Phys. J. Appl. Phys.

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“…This underlines the importance of the absence of m-SWNT and nanoparticles in a sample on the optical gain properties: indeed, sample A was only constituted by s-SWNT in PFO [12,17]. In order to provide an estimation of the overall optical losses α, the Shifting Excitation Spot (SES) method was used [24]. Furthermore, this method allows a scan of the VSL strip length with a constant size excitation spot and is able to demonstrate the homogeneity of the thin SWNT based layer.…”

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confidence: 99%

Optical gain in carbon nanotubes

Gaufrès

Izard

Roux

et al. 2010

Applied Physics Letters

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Semiconducting single wall carbon nanotubes (s-SWNT) have proved to be promising material for nanophotonics and optoelectronics. Due to the possibility of tuning their direct band gap and controlling excitonic recombinations in the near-infrared wavelength range, s-SWNT can be used as efficient light emitters. We report the first experimental demonstration of room temperature intrinsic optical gain as high as 190 cm −1 at a wavelength of 1.3 µm in a thin film doped with (8,7) s-SWNT. These results constitute a significant milestone towards the development of laser sources based on carbon nanotubes for future high performance integrated circuits. [4]. Luminescence properties of carbon nanotubes attracted a special interest, and became a leading component in various configurations, not only as individualised entities in micelle surfactant, but also when suspended over trenches [8] or deposited onto chip surface [9]. Numerous works prove that the nanotube environment plays a primordial role in their emission behaviour [10][11][12], and several nonradiative de-excitation mechanisms exist, either by Auger recombination [13] or energy transfers to metallic SWNT (m-SWNT) [14] or excitons [15]. These mechanisms lead to a strong competition between bright and dark excitons and a limited photoluminescence lifetime [16]. Up to now, a main challenge was to obtain light amplification in carbon nanotubes. Here, we experimentally demonstrate optical gain in carbon nanotubes at a wavelength of 1.3 µm at room temperature. Semiconducting SWNT (s-SWNT) extracted by the previously described polyfluorene (PFO) method [17] were drop cast on glass substrate. Pure s-SWNT thin films will be hereafter designated as sample A, while a control sample made with a blend of s-and m-SWNT will be named sample B. Both layers have a homogeneous carbon nanotube density and a thickness of 1 µm. The coating was made to obtain regular and vertical edge facets [18]. Absorbance spectrum of such initial s-SWNT/PFO solution and photoluminescence spectrum of drop-casted s-SWNT/PFO solution on glass substrate are reported in ref 12. Optical properties characterized by the E 22 and E 11 optical transitions are related to strongly bound excitons [19]. Photons absorbed on the E 22 optical transition create excitons at the carbon nanotube surface and light emission is produced due to the exciton recombination through the E 11 optical transi- tion. The polymer host matrix (PFO) presents absorption and photoluminescence peaks in the UV-visible spectrum range, and is optically inactive (no absorption and no emission) on the near infrared carbon nanotube absorption and emission range, without any evidence of energy transfer towards carbon nanotubes [20].Optical gain measurements were first performed on sample A using the variable strip length (VSL) method [21]. The sample was optically excited by an Optical Parametric Oscillator laser emitting at a wavelength of 740 nm, pumped by a two nanosecond pulsed Nd:YAG laser at 355 nm. Amplified Spontaneous Emission (ASE) ...

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“…One of the drawbacks of the ͗l /2l͘ method is that it requires two data points eventually too far apart from each other, which will be discussed below. This often leads to gain saturation, 11,13 and the gain value is underestimated. On the other hand, the advantage of this method is the existence of an analytical solution to the equation.…”

mentioning

confidence: 99%

“…Diffraction effects cause spatially inhomogeneously illuminated stripe edges for small stripe lengths and thereby produce artificial modulations in the emission spectrum. 11,15 Diffraction itself can only be reduced, e.g., by placing the sample as close as possible behind the apertures that constrain the stripe. Therefore, a method insensitive to diffraction is presented, referred to as the ͗difflog͘ method.…”

mentioning

confidence: 99%