Fig. 1. Absorption spectra of Nd(TTA)₃DBTDPO powder and NdCl₃·6H₂O powder

Fig. 2. Emission spectra of Nd(TTA)₃DBTDPO doped PMMA film pumped by 405 nm LEDs with different powers

Fig. 3. Characterizations of waveguide structure. (a) Section view of BK-7 glass waveguide; (b) section view of SU-8 polymer waveguide; (c) top SEM view of BK-7 glass waveguide; (d) section view of SU-8 polymer waveguide covering active upper cladding

Fig. 4. Measurement system for gain performance. (a) Diagram of experimental setup; (b) diagram of signal light transmission in evanescent waveguide

Fig. 5. Test results for gain in BK-7 glass waveguide. (a) Relationship between output signal intensity and pump power when 405 nm LED is used for pumping; (b) relationship between relative optical gain and pump power when LEDs with different wavelengths are used for pumping; (c) spectra of LED pump light at different wavelengths

Fig. 6. Change of signal intensity at waveguide output end before and after 405 nm LED pumping

Fig. 7. Schematics of energy level transition of Nd³⁺ ions. (a) Schematic of energy transfer system for organic ligand and Nd ³⁺ ion; (b) schematic of Nd³⁺ ion transition under pumping of different LEDs