The recently released Planck data , emphasize that the background geometry of inflation is not pure de Sitter , but from the slow variation of Hubble parameter during the inflationary era , it can be quasi-de Sitter .
This motivates us to consider an asymptotic de Sitter mode function for reconstruction of initial mode and primordial power spectrum of curvature perturbation .
Using Markov Chain Monte Carlo ( MCMC ) method together with applying recent observational constraints from the Cosmic Microwave Background ( CMB ) data for our parameterized asymptotic initial mode shows some deviation from pure de Sitter or Bunch-Davies mode .
Based on Planck 2015 data release the amplitude of scalar perturbations in 68 \% confidence level is 10 ^ { 9 } A _ { s } = 2.94 ^ { +0.42 } _ { -0.42 } and deviation from Bunch-Davies mode is \sim 0.05 - 0.06 .
In this parametrization , the CMB power spectrum of our model shows more red-tilt in comparison with \LambdaCDM model .
Furthermore , we found upper limit for tensor-to-scaler ratio with different pivot scales r _ { 0.05 } < 0.059 and r _ { 0.002 } < 0.006 .