How to fit two separate variables with smoothing spline, Gauusian or polynomial?

I have these two variables and want to fit and plot them.

lam = [0.30,0.31,0.32,0.33,0.34,0.35,0.36,0.38,0.39,0.41,0.43,0.45,0.47,0.49,0.52,0.54,0.58,0.61 ] * 10^-6;                                      % wavelength
sz_prmt = ((2*pi*rad)./lam);
scblk = [1.5805,1.5503,1.5115,1.4653,1.4006,1.3323,1.3072,1.2224,1.1680,1.0444,0.9153,0.8097,0.7010,0.7678,1.3471,1.3397,0.7991,0.5117];