Has anyone developed tunable notch filters in the visible RGB wavelengths which have very fast response times? I am interested in whether the combination of a spectrometer and a tunable notch filter with notch frequencies at the visible red, green and blue wavelengths which have very fast response times could be used to deflect laser beams aimed at airplane windows. The purpose of the spectrometer is to detect the wavelength(lambda) of the incoming laser beam and then tune the optical notch filter to the notch wavelength lambda. 
I am currently reading a paper, 

Independently tunable optical notch filter based on double ring resonator structure,  J. Zhang, S. Guo, X. Li. Optik 124 no. 12 (2013), pp.1307-1310. 

This paper describes a tunable optical notch filter based on the Mach-Zehnder interferometer (MZI) with cascaded double ring resonator structures. Does anyone know whether the optical notch filter described in this paper could be used to deflect red, green or blue laser beams aimed at airplane windows?
I am also reading a paper, 

Demonstration of a Tunable Microwave-Photonic Notch Filter Using Low-Loss Silicon Ring Resonators, M. Rasras, et al. J. Lightwave Technol. 27 no. 12 (2009), p. 2105.

This paper discusses how to use thermo-optic phase shifters to set the coupling ratios, all pass filter phases and the Mach-Zehnder input-output couplers. While thermo-optic phase shifters can be tuned in milliseconds, subnanosecond tuning speeds should be achievable using technology currently being explored for the high-speed modulators such as carrier injection or carrier depletion in a reversed biased junction. The tuning speed must be fast as possible for the laser beam deflector to react as fast as possible to laser beams aimed at airplane windows
 A: Generally speaking, tunable filters are not appropriate for airplane windows.
Optical notch rejection filters are based upon phase matching conditions.  These phase matching conditions created by quarter-wave layers (e.g. see Thin-Film Optical Filters, by H.A. Macleod, for information on how to design thin film stacks).  It is common for these filters to be sensitive to both wavelength and angle.  So, a notch filter typically rejects a specific wavelength and a specific angle.
So, from a conventional thin film stack point of view, coatings can only reject a specific wavelength at a specific incident angle.
Next, consider the agile optical filter.  This is typically created by changing the optical path length between two reflective layers.  For example, a geometry that is similar to an airplane window would be a liquid crystal tunable filter or an electro-optic cell.
The LCTF (liquid crystal tunable filter) operates as a Fabry-Perot cavity (see this device for an example).  This configuration transmits a series of narrow bands rather than rejecting a series of narrow bands.
Let's assume you get over this hurdle with the appropriate coatings.  The geometry looks right (plane-parallel window) and you can reject the wavelengths you want.  Let's also assume that your spectrometer is fast enough (pretty easy to do assuming the wavelength ranges are well known).  Now you need to contend with speed.
In a plane-parallel configuration, any electro-optic type of filter will appear as a capacitor.  The capacitance will determine the speed.  Capacitance increases linearly with area and decreases with thickness.  So, you need to generally divide up the area of the window into pixels so you have an array of capacitors rather than one big capacitor the size of the windshield.
To put this in perspective, 25 mm diameter LCTF's can operate in the kHz range.  If you need to cover a windshield that is 250 mm in diameter, the operating frequency will drop by 10X.
Bear in mind that a more efficient solution may be a visor on a helmet rather than a windshield.
As you consider the possibilities, look at devices and projects like the following:


*

*Gentex Laser Visor

*Adaptive Agile Multi-Spectral Laser Protection Devices by Kent Optronics

*Kent Optronics Laser Protection
This is not a new problem and many have tried to address it with a variety of approaches.
A: I think people typically use conducting electrodes for window-sized areas, such as Indium Tin Oxide. If you want to tune the whole window at once, then maybe you can get away with just one large pair of electrodes with the nanosphere material sandwiched in-between. 
