Embedded　microball　lenses　with　superior　optical　properties　function　as　convex　microball　lens　(VMBL)　and　concave　microball　lens　(CMBL)　were　fabricated　inside　a　PMMA　substrate　with　a　high　repetition　rate　femtosecond　fiber　laser.　The　VMBL　was　created　by　femtosecond　laserinduced　refractive　index　change,　while　the　CMBL　was　fabricated　due　to　the　heat　accumulation　effect　of　the　successive　laser　pulses　irradiation　at　a　high　repetition　rate.　The　processing　window　for　both　types　of　the　lenses　was　studied　and　optimized,　and　the　optical　properties　were　also　tested　by　imaging　a　remote　object　with　an　inverted　microscope.　In　order　to　obtain　the　microball　lenses　with　adjustable　focal　lengths　and　suppressed　optical　aberration,　a　shape　control　method　was　thus　proposed　and　examined　with　experiments　and　ZEMAX　(R)　simulations.　Applying　the　optimized　fabrication　conditions,　two　types　of　the　embedded　microball　lenses　arrays　were　fabricated　and　then　tested　with　imaging　experiments.　This　technology　allows　the　direct　fabrication　of　microlens　inside　transparent　bulk　polymer　material　which　has　great　application　potential　in　multi-function　integrated　microfluidic　devices.　(C)　2015　Optical　Society　of　America