High-gain organic semiconductor Raman active medium laser device and application thereof

Abstract

The invention belongs to the technical field of laser, and discloses a high-gain organic semiconductor Raman active medium laser device and application thereof. The device comprises a substrate and an organic semiconductor Raman active medium, wherein the Raman active medium is uniformly deposited on the substrate; the organic semiconductor Raman active medium is pi-conjugated organic small molecules or polymers or a mixture of the materials. Pumping laser lasing is carried out on the prepared device, a Raman signal generated by pumping needs to be matched with stimulated radiation, namely amplified spontaneous emission (ASE) or a laser wavelength area, and therefore a stimulated Raman scattering (SRS) signal is generated. Molecular vibration in an organic semiconductor can be remarkably amplified without an optical microcavity, an ultra-low Raman threshold value is achieved in the organic semiconductor, and an obtained SRS signal has the broadband spectrum tunable characteristic. The method provided by the invention is low in cost and rapid in preparation method, and can be applied to compact and efficient organic Raman amplifiers and lasers.

Description

Technical Field

[0001] The present invention belongs to the field of laser technology, and particularly relates to a method for achieving efficient Raman response in organic semiconductors, namely spectral tailored gain-induced stimulated Raman scattering (STGI-SRS). This strategy provides sufficient optical gain to achieve an ultra-low Raman threshold in organic semiconductors, and the stimulated Raman scattering (SRS) signal obtained by this method has wide spectral tuning characteristics. Background Art

[0002] Nonlinear optical phenomena have attracted widespread attention due to their alteration of light characteristics, and they are the basis of nonlinear spectroscopy, frequency conversion, and new light sources, etc. The development of laser technology has greatly promoted the progress of SRS. It generates optical gain by making a constant change in the frequency of the incident light, and this frequency change matches a constant frequency difference generated by molecular or atomic vibrations. Due to its unique vibration signal and convenient spectral tuning ability, SRS has been widely applied in frontier optical fields such as Raman lasers, coherent Raman scattering microscopes, and silicon-based optoelectronics. Although SRS has been reported in many materials, compared with the optical gain generated by radiative transitions in optical materials, the gain corresponding to the SRS process in Raman active media is much smaller. Currently, in Raman laser technology, a common method to enhance Raman gain is to use an optical cavity with a high quality factor (Q) to enhance the interaction between light and matter, thereby increasing the net Raman gain. However, the selection of the pump source and Raman gain medium is severely restricted by the cavity structure.

[0003] Since the first discovery of carbon-based conductive materials (now commonly referred to as organic semiconductors) in 1977, they have exhibited unique semiconductor characteristics related to the delocalization of π electrons in molecular chains. The optoelectronic properties of these semiconductors can be adjusted by changing the chemical structure, and they are compatible with many substrates. Therefore, organic semiconductors have been applied in many optoelectronic devices, including organic light-emitting diodes, solar cells, transistors, and lasers. However, the optical damage threshold of organic semiconductors is relatively low, making it difficult to apply them in nonlinear optical devices such as SRS. Stimulated emission-mediated SRS provides an effective method to amplify Raman signals and reduce the SRS threshold. By combining the additional gain from electronic resonance, a significant enhancement of the overall Raman performance can be achieved. Especially when the main Raman mode overlaps with the electronic resonance region (such as amplified spontaneous emission, i.e., ASE or laser), the Raman intensity increases exponentially, and this gain can be achieved without a high-Q optical cavity. However, due to the overlapping noise from stimulated emission, the signal-to-noise ratio (SNR) of the Raman signal has always been very low, usually less than 10 dB. In addition, the wavelength tuning range of SRS is limited by the gain bandwidth of organic semiconductors, usually within 30 nm or even smaller. So far, it is still very difficult to achieve efficient nonlinear Raman response in organic semiconductors. Summary of the Invention

[0004] The object of the present invention is to provide a method for achieving efficient Raman response in organic semiconductors, so as to solve the problems that it is difficult to construct Raman amplifiers and lasers in current organic semiconductors due to their low optical damage thresholds.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A high-gain organic semiconductor Raman active medium laser device, the device includes a substrate and an organic semiconductor Raman active medium, and the Raman active medium is uniformly deposited on the substrate. The organic semiconductor Raman active medium is a π-conjugated organic small molecule or polymer, or a mixture of the above materials.

[0007] Preferably, the substrate is one of a quartz substrate, glass, a silicon wafer or a flexible substrate.

[0008] Preferably, the deposition method of the organic semiconductor Raman active medium is one of spin coating, inkjet printing or vacuum evaporation.

[0009] Preferably, the thickness of the organic semiconductor Raman gain medium is 80 - 240 nm.

[0010] The present invention also provides the application of the above high-gain organic semiconductor Raman active medium laser device, which can be applied to an organic Raman amplifier or an organic Raman laser.

[0011] Preferably, the prepared organic semiconductor Raman active medium laser device is pumped for laser lasing, and the Raman signal generated by the pump needs to match the stimulated emission, that is, the ASE or laser wavelength region, so as to generate multi-order SRS signals.

[0012] In the above technical solution, the organic semiconductor Raman active medium needs to have optical gain generated by stimulated emission, and the spectral range of the optical gain generated by stimulated emission matches the Raman signal wavelength region. As Figure 15 shown, the Raman signals generated by the laser device prepared with the organic semiconductor Raman active medium are multiple amplified cascaded Raman signals. The pump light is introduced into the waveguide structure of the organic semiconductor to generate optical gain, and the local electromagnetic field at the Stokes shift is significantly enhanced by stimulated emission-mediated, thereby exciting the SRS process. By simultaneously ensuring the processes of stimulated emission and Raman excitation through the high optical gain generated by stimulated emission, the spectral matching between the Raman peak position and stimulated emission, the strong Raman vibration signal, and the appropriate absorption ability during the pumping process, STGI-SRS is realized in the organic semiconductor, thus achieving efficient and cascaded nonlinear Raman response. Without an optical microcavity, the molecular vibration in the organic semiconductor can be significantly amplified, and an ultra-low Raman threshold is achieved in the organic semiconductor, and the SRS signal obtained by this method has the characteristic of wide spectral tunability.

[0013] The technical solution of the present invention has the following beneficial effects: The present invention provides a method for achieving efficient Raman response in organic semiconductors, effectively solving the problems that it is difficult to construct organic Raman amplifiers and lasers due to the low optical damage threshold of current organic semiconductors. This method provides sufficient optical gain, thereby achieving an ultra-low Raman threshold in organic semiconductors. The SRS signal obtained by this method has the characteristics of wide wavelength tuning and has a bright application prospect. The method of the present invention is low in cost and fast in preparation method, and can be applied to compact and efficient organic Raman amplifiers and lasers. Description of the Drawings

[0014] Figure 1 is the chemical structural formula of poly[9,9-dioctylfluorene-2,7-diyl] (PFO);

[0015] Figure 2 is the relationship between the thresholds of the first to third order STGI-SRS signals of the PFO thin film and the pump wavelength and the tuning range of the emission wavelength;

[0016] Figure 3 is the dependence relationship between the thresholds of the first to third order STGI-SRS signals of the PFO thin film and the absorption coefficient;

[0017] Figure 4 is the pump energy dependence curve of PL / ASE and the first order STGI-SRS signal of the PFO thin film under 420nm excitation;

[0018] Figure 5 is the pump energy dependence curve of the second and third order STGI-SRS signals of the PFO thin film under 420nm excitation;

[0019] Figure 6 is the spectral signal of PL / ASE and the first order STGI-SRS of the PFO thin film as a function of pump energy under 420nm excitation;

[0020] Figure 7 is the spectral signal of the second order STGI-SRS of the PFO thin film as a function of pump energy under 420nm excitation;

[0021] Figure 8 is the spectral signal of the third order STGI-SRS of the PFO thin film as a function of pump energy under 420nm excitation;

[0022] Figure 9 is the chemical structural formula of the ladder compound A;

[0023] Figure 10 is the relationship between the thresholds of the first to third order STGI-SRS signals of the ladder compound A thin film and the pump wavelength and the tuning range of the emission wavelength;

[0024] Figure 11 is the dependence of the threshold of the first to third order STGI-SRS signal on the absorption coefficient of the ladder compound A film;

[0025] Figure 12 The pump energy dependence curves of PL / ASE and first-order STGI-SRS signal of the ladder-shaped compound A film under 450nm excitation;

[0026] Figure 13 The pump energy dependence curves of the second-order and third-order STGI-SRS signals of the ladder compound A film under 450nm excitation;

[0027] Figure 14 The spectral signals of PL / ASE and first-order STGI-SRS signals of ladder-shaped compound A film under 450nm excitation as a function of pump energy;

[0028] Figure 15 Schematic diagram of gain-induced stimulated Raman scattering tailored for spectroscopy. DETAILED DESCRIPTION

[0029] The present invention is further described below through several embodiments and drawings, but it should be clear that the following embodiments are only partial implementation methods of the technical solution of the present invention with better effects, and do not limit the scope of the technical solution of the present invention.

[0030] Embodiment 1:

[0031] The present embodiment relates to a high-gain organic semiconductor Raman-active medium laser device and an application thereof. The organic semiconductor Raman-active medium laser device is prepared by: selecting a transparent quartz sheet as a substrate and selecting PFO as an organic semiconductor Raman gain medium; using toluene as a solvent to prepare a PFO organic solution with a concentration of 15 mg / mL; using spin coating as a deposition method of the organic semiconductor Raman-active medium, wherein the spin coating speed is 2000 rpm, the spin coating time is 60 s, the spin coating acceleration is 500 rpm / s, and the prepared film thickness is 128 nm.

[0032] The prepared PFO laser device was irradiated with pump laser: a 10 Hz, 5 ns neodymium-doped yttrium aluminum garnet (Nd:YAG) laser was used as the pump source for excitation, and an optical parametric oscillator (OPO) was used to tune the pump wavelength. The area of stimulated radiation was 0.018 cm -1 The ASE threshold was measured to be 8.8 μJ / cm 2 . 150~180μJ / cm 2 At a pump flux of 1.5, the peak net gain coefficient of PFO is 50.3 cm -1 , the fluorescence quantum yield is 42%.

[0033] in, Figure 1 The molecular structure of PFO is shown. Figure 2 The relationship between the threshold of the first to third order STGI-SRS signal of PFO and the pump wavelength and the tuning range of the emission wavelength are shown. The pump wavelength range is 410-428nm with an interval of 2nm. Figure 3 The relationship between the threshold and absorption factor of the first to third order STGI-SRS signals of PFO is shown in Figure 1. The output and spectral curves of the first to third order STGI-SRS signals under 420nm excitation conditions are shown in Figure 2. Figures 4 - 8 shown.

[0034] Embodiment 2:

[0035] The present embodiment relates to a high-gain organic semiconductor Raman-active medium laser device and an application thereof. The organic semiconductor Raman-active medium laser device is prepared by: selecting a transparent quartz sheet as a substrate, selecting a trapezoidal compound A as an organic semiconductor Raman gain medium; using toluene as a solvent, preparing an organic solution of the trapezoidal compound A with a concentration of 25 mg / mL; using spin coating as a deposition method of the organic semiconductor Raman-active medium, wherein the spin coating speed is 2000 rpm, the spin coating time is 60 s, the spin coating acceleration is 500 rpm / s, and the prepared film thickness is 134 nm.

[0036] The prepared trapezoidal compound A laser device was irradiated with pump laser: a 10 Hz, 5 ns Nd:YAG laser was used as the pump source for excitation, and an OPO was added to tune the pump wavelength. The area of stimulated radiation was 0.018 cm -1 The ASE threshold was measured to be 5.6 μJ / cm 2 . 150~180μJ / cm 2 At a pump flux of , the peak net gain coefficient of SpL(2)-1 is 131.6 cm -1 , the fluorescence quantum yield is 12%.

[0037] in, Figure 9 is the molecular structure of compound A. Figure 10 The relationship between the threshold of the first to third order STGI-SRS signal and the pump wavelength and the tuning range of the emission wavelength of compound A are shown in FIG. Figure 11 The relationship between the threshold and absorption factor of the first to third order STGI-SRS signal of compound A. The output and spectral curves of the first to third order STGI-SRS signal under 450nm excitation conditions are shown in Figures 12 - 14 shown.

Claims

1. A high-gain organic semiconductor Raman active medium laser device, characterized in that: The device includes a substrate and an organic semiconductor Raman active medium, and the Raman active medium is uniformly deposited on the substrate; the organic semiconductor Raman active medium is a π-conjugated organic small molecule or polymer, or a mixture of the above materials.

2. The high-gain organic semiconductor Raman active medium laser device according to claim 1, characterized in that: When the organic semiconductor Raman active medium laser device is pumped for laser emission, if the Raman signal generated by the pump matches the stimulated emission, that is, the ASE or the laser wavelength region, multi-order SRS signals can be generated.

3. The high-gain organic semiconductor Raman active medium laser device according to claim 1, characterized in that: The substrate is one of a quartz substrate, glass, a silicon wafer, or a flexible substrate.

4. The high-gain organic semiconductor Raman active medium laser device according to claim 1, wherein: The deposition method of the organic semiconductor Raman active medium is one of spin coating, inkjet printing, or vacuum evaporation.

5. The high-gain organic semiconductor Raman active medium laser device according to claim 1, characterized in that: The preferred thickness of the organic semiconductor Raman gain medium is 80 - 240 nm.

6. Application of a high-gain organic semiconductor Raman active medium laser device as described in any one of claims 1-5, characterized in that, It can be applied to an organic Raman amplifier or an organic Raman laser.

7. The application of the high-gain organic semiconductor Raman active medium laser device according to claim 6, characterized in that: The prepared organic semiconductor Raman active medium laser device is pumped for laser emission, and the Raman signal generated by the pump needs to match the stimulated emission, that is, the ASE or the laser wavelength region, so as to generate multi-order SRS signals.

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