Holographic polymer networks formed in liquid crystal phase modulators via a He-Ne laser to achieve ultra-fast optical response

Abstract

The holographic polymer network formed in liquid crystal (LC) phase modulators via a He-Ne laser in this study demonstrates ultra-fast optically response and low light scattering. These advantages are mainly caused by the small LC domains and uniform polymer network when processing LC cells via holographic exposure to a He-Ne laser. The use of this method to fabricate LC cells as phase modulators results in a decay time of 49 μs under 2π phase modulation at room temperature. The predicted fast optical response can be achieved when operating devices at high temperatures.

Doping Liquid Crystal Cells with Photocurable Monomer via Holographic Exposure to Realize Optical-Scattering-Free Infrared Phase Modulators with Fast Response Time

“…Due to short operation time in real phase modulations, the polymer networks were not seriously deformed to induce unstable phase modulation control as previously described. The ideal and correct phase modulations can be achieved with higher applied voltages [13] or a longer waiting time (about a few seconds) [20]. In this study, we applied voltages of 84, 110, and 135 V rms to ideally achieve the 1.0π, 1.5π, and 2.0π phase modulations as shown in Figure 6b.…”

“…Therefore, the interference patterns generated by holographic exposure will possibly lead to the formed morphology of holographic polymer networks in PLNC cells as schematically shown in Figure 1c. Finally, the smaller LC domains are embedded in polymer networks to achieve light scattering reduction [13]. Figure 2 shows the setup used to measure the relative curves of voltage versus optical reflectance (V-R) of completely exposed PNLC cells.…”

“…However, light scattering occurs due to the refractive index mismatch of polymer networks and LC microdomains [1]. The degree of light scattering can be reduced by using much smaller LC microdomains via optimal processing conditions such as monomer concentrations and photopolymerization conditions [9][10][11][12][13]. Several studies have demonstrated scattering-free PNLC phase modulators at near infrared wavelength [14][15][16][17].…”

“…Many studies used this process to fabricate optical-scattering-free electro-optical LC devices such as holographic polymer-dispersed LCs [18] and polymer LC polymer slices [19]. In our previous work, we adopted the holographic exposure via a low-power He-Ne laser to expose the anisotropic monomer RM257-doped LC cells to generate holographic polymer networks and to realize a LC phase modulator with low light scattering and ultra-fast response time at visible wavelengths [13]. However, the operating voltage (185 V rms ) was not suitable for conventional operations.…”

A He-Ne gas laser with tunable wavelength and stable output intensity based on photon tunneling

“…[1][2][3][4][5][6] In some practical applications, for example, absorption spectroscopy, the wavelength and intensity modulations of lasers are needed. [7][8][9][10] Our designed laser has the potential to be applied in this field and may inspire researchers to use this intensity modulation method in other lasers.…”