Posted: July 7th, 2015

Measuring the Decay Length

Results

Measuring the Decay Length

The decay length was measured when the excitation polarization is along and perpendicular to the waveguides and when it is 45 °.

The equation (1) is used to measure the decay the intensity as shown in Figure 1.

(1)

 

 

 

figure 1

 

 

 

 

The decay length when the single is polarized along the waveguide (θ = 0°)

 

Figure 2 Plot of intensity with the increase of length

 

Following are the calculations to find the maximum waveguide limit,

I = 0.6978e^-0.093L

I = I₀^-L/L₀

 

Where L_o is the decay length, which is calculated, and I_o is the laser intensity.

From the above calculations we can infer that waveguide will not propagate more than

 

 

 

The decay length when the single is polarized perpendicular the waveguide (θ = 45°)

 

 

I = 0.4937e^-0.093L

I = I₀^-L/L₀

 

 

 

 

 

 

 

 

 

 

 

 

The decay length when the single is polarized perpendicular the waveguide (θ = 90°)

 

 

I = 0.2039e^-0.165L

From the above calculations we can infer that waveguide will not propagate more than

When the waveguide is excited by light polarized along the waveguide, it will propagate 4 times more than when it is perpendicular to the waveguide.

 

The plasmonic modes

There different modes.

• When the light was focused along the waveguide
• When the light was polarized by 45
• When the light was polarized perpendicular to the waveguide.

 

 

 

 

 

 

 

Intensity Dependence on the Polarization of the Light

When the excitation polarizations varied from 0 to 90, the coupling to the branch wire starts.

 

 

 

Intensity and Power in Relation With Polarization of a Plasmonic Waveguide

The intensity is plotted as a function of incident polarization angle. The graphical plots below shows the intensity and the power at different polarizations, respectively.

 

Figure 12 Intensity as a function of incident polarization angle

 

 

Figure 13 Power as a function of incident polarization angle

 

 

θ is the input polarization, I₁ and P₁ are the intensity and the power outflow at the end of the branch wire, respectively. I₂ and P₂ are the intensity and power at the end of the main wire, respectively.

Plasmonic modes with branches

E_y component, E_y component

 

 

 

 

 

 

 

 

 

 

Changing the branching angles

The long waveguide is the main wire I₂, and the small waveguide is the branch wire I₁.

– When the laser was polarized along the waveguide θ = 0°, the branch angle was varied from 10° to 90°

 

 

 

the intensity as a function of the branch angle

 

 

The power as a function of the branch angle

 

• When the laser was polarized perpendicular to the waveguide θ = 90°, the branch angle was varied from 10° to 90°

 

 

 

 

 

 

 

 

The intensity as a function of the branch angle

 

 

The power as a function of the branch angle

 

When the laser was polarized along the waveguide θ = 45°, the branch angle was varied from 10° to 90°

 

 

 

 

 

 

 

 

 

 

 

Changing the position of the branch wire:

• The incident light was polarized along the waveguide (θ = 0°) and the branch angle was at 90° to the main wire. The position of the branch wire was changed from 0.4 µm 30 times by 20 nm.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

• The incident light was polarized perpendicular the waveguide (θ = 90°) and the branch angle was at 90° to the main wire. The position of the branch wire was changed from 0.4 µm 30 times by 20 nm.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

– The incident light was polarized by (θ = 45°) and the branch angle was at 90° to the main wire. The position of the branch wire was changed from 0.4 µm 30 times by 20 nm.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Changing the wavelength

The wavelength (λ) was varied from 0.65 nm to 0.75 nm. λ