Hi, I am analyzing the paper for my thesis and have

Equation

IF=-1*(1+cos(δ))*cot(θ)*σ_2-sin(δ)*cot(θ)*σ_1

where σ_1={{0,1},{1,0}} and σ_2={{0,-i},{i,0}} are the Pauli matrices

The component σ_1 is diagonal in the (1/√2, +/- 1/√2) linear polarization basis and the component σ_2 is diagonal in the circular polarization basis (1/√2, +/- i/√2).

What is mathematical representation of σ_1 and σ_2 being diagonal in that basis.

Thanks in advance,

vredina97