Amplified Spontaneous Emission Threshold Dependence on Determination Method in Dye-Doped Polymer and Lead Halide Perovskite Waveguides

Abstract

Nowadays, the search for novel active materials for laser devices is proceeding faster and faster thanks to the development of innovative materials able to combine excellent stimulated emission properties with low-cost synthesis and processing techniques. In this context, amplified spontaneous emission (ASE) properties are typically investigated to characterize the potentiality of a novel material for lasers, and a low ASE threshold is used as the key parameter to select the best candidate. However, several different methods are currently used to define the ASE threshold, hindering meaningful comparisons among various materials. In this work, we quantitatively investigate the ASE threshold dependence on the method used to determine it in thin films of dye-polymer blends and lead halide perovskites. We observe a systematic ASE threshold dependence on the method for all the different tested materials, and demonstrate that the best method choice depends on the kind of information one wants to extract. In particular, the methods that provide the lowest ASE threshold values are able to detect the excitation regime of early-stage ASE, whereas methods that are mostly spread in the literature return higher thresholds, detecting the excitation regime in which ASE becomes the dominant process in the sample emission. Finally, we propose a standard procedure to properly characterize the ASE threshold, in order to allow comparisons between different materials.

Donor–acceptor naphthalimides and peryleneimides for all-solution-processed thin film lasers

“…S6 in ESI †). 42 The behavior observed in Fig. 2b is the typical one for dye-doped systems: the threshold decreases upon the concentration increases until a certain concentration at which it starts rising, normally because of concentration-quenching effects.…”

Distributed Feedback Lasers by Thermal Nanoimprint of Perovskites Using Gelatin Gratings

“…The threshold behavior of the laser device is presented in Figure b which shows the maximum output intensity as a function of the pump fluence. The lasing onset is recognized by slope change in the lasing input–output characteristics due to the transition from spontaneous to stimulated emission . We define the lasing threshold at the intersection of the two linear fits of the below and above threshold emission, which gives a threshold of 81 μJ/cm 2 (Figure b).…”

“…The lasing onset is recognized by slope change in the lasing input–output characteristics due to the transition from spontaneous to stimulated emission. 66 We define the lasing threshold at the intersection of the two linear fits of the below and above threshold emission, which gives a threshold of 81 μJ/cm 2 ( Figure 3 b). This threshold is an acceptable value compared to the reported values so far (in the range of approximately tenths of μJ/cm 2 ) and even outperforms some DFBs relying on more complex fabrication techniques including EBL, RIE, or IBE ( Table S1 and Figure S7 ).…”

Temperature-Dependent Amplified Spontaneous Emission in CsPbBr3 Thin Films Deposited by Single-Step RF-Magnetron Sputtering

“…In particular, the ASE threshold was defined as the excitation density at which the spectral shape starts to change due to the appearance of an ASE band. This procedure, known as the visual method [ 36 ], seems to be the best one to provide the lowest threshold values due to the appearance of the early stage ASE emission in a straightforward way.…”