# Fourier expansion of the Klein-Gordon field

Is there a reason(both physical and mathematical) why the Klein-Gordon field is represented as a fourier expansion in the second quantization as opposed to other mathematical expansions? Be gentle with the answers!

• What do you mean by represented? It solves a wave equation, so it has nice Fourier modes. Also, what is your precise notion of second quantization? QFT, i.e. quantizing the fields as opposed to quantizing $x$ and $p$? – ACuriousMind Jul 11 '14 at 15:11
• Also, it is easiest to quantize decoupled oscillators. By going to Fourier space, all the modes are decoupled, and the expansion coefficients are easily seen to satisfy the standard SHO algebra. – QuantumDot Jul 11 '14 at 15:22