A photonic‐microfluidic integrated device is demonstrated with excellent and reliable fluorescence detection performance. CV values of 8% for 2.5‐μm beads and 14% for 6‐μm beads were achieved through the correct deployment of carefully formed excitation beam shapes via integrated on‐chip optics even without the use of 3D hydrodynamic focusing or a high‐quality laser source and single mode beam propagation. The devices are fabricated in a monolithic planar fashion using a system of microlenses and waveguides integrated with microfluidic channels on‐chip and packaged using a high‐quality and low‐cost channel sealing and high‐performance interconnecting technology developed from our earlier works. Beam geometry in the excitation region is shown to affect the variation of fluorescence intensity from specimens, hence configurations of beam geometry targeted for a specific bead sizes are examined to ensure proper deployment of the lens designs. The formed high‐quality optical excitation regions ensure reliable detection even with relaxed hydrodynamic focusing to ensure applicability with multiple specimen sizes. Device performance with each bead size was found to be acceptable for a range of beam geometries with a different ideal configuration for each bead size. These device designs help to form a device that will supplement conventional flow cytometry in point‐of‐care and remote detection applications by performing specific detections with an inexpensive and replaceable device.