As a Mechanical Development Engineer( Hydrophone Sensor) at Optics11, you contribute to the development and engineering realization of the hydrophone sensor subsystem throughout the product development lifecycle. You translate allocated product and subsystem requirements into robust engineering solutions while developing your technical expertise in underwater sensor technology. The hydrophone sensor subsystem comprises the acoustic sensing element, mechanical housing, internal structural components, sealing concepts, and associated mechanical interfaces that enable reliable underwater sensing performance. Working as part of a multidisciplinary engineering team, you contribute to developing, improving, and maturing subsystem solutions that support successful product realization. You work closely with Product System Engineering, Product Integration, Verification & Validation, Lifecycle Engineering, manufacturing partners, and other subsystem development teams to develop reliable hydrophone sensor solutions while continuously expanding your technical capability. Key Responsibilities: • Contribute to the development and realization of the hydrophone sensor subsystem throughout the product development lifecycle. • Translate product and subsystem requirements into robust engineering solutions. • Develop hydrophone sensor assemblies, mechanical housings, internal structures, sealing concepts, and subsystem interfaces. • Produce detailed mechanical designs, engineering drawings, specifications, calculations, and design documentation. • Develop prototypes and support subsystem integration, testing, and verification activities. • Perform engineering analysis, characterization, and validation of hydrophone sensor assemblies. • Support acoustic characterization and correlate engineering models with experimental results. • Analyze engineering results, identify technical issues, and implement design improvements. • Apply engineering expertise in precision mechanical design, fiber-optic sensing technology, materials, sealing, and structural design. • Contribute to technical trade-off studies, design reviews, and multidisciplinary engineering discussions. • Support root cause investigations and implement corrective engineering solutions. • Improve subsystem robustness, manufacturability, maintainability, reliability, and production readiness. • Plan and execute assigned engineering activities within agreed priorities and timelines. • Communicate technical progress, risks, and dependencies proactively with stakeholders. • Collaborate effectively across multidisciplinary teams and share engineering knowledge and best practices. • Ensure engineering deliverables meet quality, performance, and reliability requirements. • Contribute to the continuous improvement of engineering processes, methods, and product quality. Why Join Us? • Join one of Europe’s most promising deep-tech scale-ups. • Shape the future of a rapidly growing multidisciplinary R&D organization. • Competitive salary and benefits package. • Enjoy regular team activities and company events. • Fresh team lunches provided 3 times/week. Qualifications: • BSc or MSc in Mechanical Engineering, Applied Physics, Precision Engineering, or a related engineering discipline.  • Approximately 2–5 years of experience in precision mechanical design, instrumentation, sensor systems, or product development.  • Experience with CAD (SolidWorks or equivalent) and engineering analysis tools, like Comsol or ANSYS. • Understanding of materials, sealing, and mechanical design principles.  • Experience with Python or similar scripting tools for engineering analysis is an advantage. • Interest in precision instrumentation, underwater sensing technologies, and multidisciplinary product development.  • Strong analytical and structured problem-solving skills. • Good written and verbal communication skills in English.  • Eligible to obtain EU/NATO security clearance.  Preferred: • Experience with fiber-optic sensors, underwater systems, or precision instrumentation.  • Familiarity with engineering testing, prototype development, or product verification.  Security & Compliance: You'll be working with clients in the defense and security sectors, obtaining a Certificate of No Objection issued by the AIVD (Dutch General Intelligence and Security Service) is mandatory. This means you will need to undergo a security screening. For more information, please refer to details on security screening.