Calculate the Doppler broadened linewidths ∆y and ∆l (end-to-end of spectrum) for the He-Ne laser transition for lo = 632.8 nm if the gas discharge temperature is about 127°C. The atomic mass of Ne is 20.2 (g mol-1). The laser tube length is 40 cm. What is the linewidth in the output wavelength spectrum? What is mode number m of the central wavelength, the separation between two consecutive modes, and how many modes do you expect within the linewidth ∆l1>2 of the optical gain curve?