Measurement and modeling of infrared nonlinear absorption coefficients and laser-induced damage thresholds in Ge and GaSb

Abstract

Using a simultaneous fitting technique to extract nonlinear absorption coefficients from data at two pulse widths, we measure two-photon and free-carrier absorption coefficients for Ge and GaSb at 2.05 and 2.5 m for the first time, to our knowledge. Results agreed well with published theory. Single-shot damage thresholds were also measured at 2.5 m and agreed well with modeled thresholds using experimentally determined parameters including nonlinear absorption coefficients and temperature dependent linear absorption. The damage threshold for a single-layer Al 2 O 3 anti-reflective coating on Ge was 55% or 35% lower than the uncoated threshold for picosecond or nanosecond pulses, respectively.

Selective enhancement of optical nonlinearity in two-dimensional organic-inorganic lead iodide perovskites

“…Our 2D perovskites however defy this universal bandgap scaling as demonstrated by the marked deviation from the red line and exhibit very strong n 2 nonlinearity when compared with other notable semiconductors 17 , 36 ( stars in Fig. 2c ): Ge has a larger n 2 value due to a much narrower bandgap (0.87 eV) but at the expense of a poor LIDT ( β ~ 70 cm GW –1 at λ = 2050 nm using 10-ps pulses) 37 ; note that Ge undergoes severe damage via one-photon absorption at typical Nd:YAG radiation ( λ = 1064 nm), which was used for accessing β in this study. For instance, the enhancement factor for n = 1 (purple diamond) is more than an order of magnitude when compared with the theoretical prediction.…”

Enhanced Ultrafast Nonlinear Optical Response in Ferrite Core/Shell Nanostructures with Excellent Optical Limiting Performance

“…Thus, diverse approaches, using different types of materials such as metallic, semiconductor or organic, are being investigated to improve their performance. However, high intensities result in photofragmentation and ligand desorption in most of these materials, resulting in irreversible material damage . Thus, exploring new materials with high stability (with higher intensity thresholds for laser‐induced thermal damage and dielectric breakdown) suitable for use in harsh/reactive environments is crucial for the development of practical devices for optical limiting applications.…”

“…Core/shell architectures have become increasingly appealing among nanomaterials to develop efficient ways to functionalize and improve the properties of single‐phase nanoparticles in distinct fields such as microelectronics, biomedicine, catalysis, optics, and magnetism, among many others . In the particular case of optical limiters, core/shell structures have been used to make certain materials stable at extreme conditions, where chemically inert oxide shells have been grown for protective purposes .…”

Двухфотонное Поглощение Излучения Нецепного HF-лазера В Монокристаллах Германия

“…Для лазерной оптики основной эффект -нелинейное поглощение на генерированных излучением неравновесных носителях заряда [3,5]. В области 2.6−5 µm на этот процесс накладываются эффекты двухфотонного [17][18][19][20][21][22][23][24][25] и трехфотонного поглощений [23]. В эксперименте эти процессы разделить крайне трудно, кроме этого, результаты исследований могут существенно зависеть от таких параметров лазерного источника, как длина волны, распределение энергии по апертуре лазерного пучка и размеров луча на кристалле Ge.…”

“…В эксперименте эти процессы разделить крайне трудно, кроме этого, результаты исследований могут существенно зависеть от таких параметров лазерного источника, как длина волны, распределение энергии по апертуре лазерного пучка и размеров луча на кристалле Ge. Поэтому корректное измерение коэффициентов поглощения для каждого процесса является сложной проблемой, и не удивительно, что величина коэффициента двухфотонного поглощения K 2 в различных работах существенно отличается (в пределах двух порядков) [17][18][19][20][21][22][23][24][25].…”