Abstract
<p>We obtained a sufficiently powerful second harmonic signal, excesses 10 mW, by doubling an external-cavity diode laser that is amplified to 95 mW by an erbium-doped fiber amplifier in a periodical poled lithium niobate waveguide to lock a frequency-doubled laser source directly to the 5S<sub>1/2</sub> <span style="font-size:12.0pt"><span style="font-family:"新細明體","serif"">→</span></span>7S<sub>1/2</sub> two photon transitions of rubidium. Our experimental scheme provides a compact, high-performance frequency standard in S-band (1460 nm ~ 1525 nm) for fiber-optic communication and sensing applications.</p>